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<!DOCTYPE html>
<html lang="en">
  <head>
    <title>API Calls Exercises in R: 17 Real-World Practice Problems</title>
    <meta charset="utf-8">
    <meta name="Description" content="R API calls exercises with httr2: 17 hands-on problems on GET/POST, headers, JSON parsing, auth, pagination, retries, and rate limit throttling.">
    <meta name="Keywords" content="R API calls exercises, httr2 R exercises, jsonlite R, REST API R, R httr2 practice, R API pagination">
    <meta name="Distribution" content="Global">
    <meta name="Author" content="Selva Prabhakaran">
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      html.dark .masthead-icon-btn{color:#b0b5bf}
      html.dark .masthead-icon-btn:hover{background:#1a1d22;color:#e8eaee}
      hr{height:0;box-sizing:content-box;border:0;border-top:1px solid #eee}
      .img-zoomable{cursor:zoom-in;transition:opacity .15s}
      .img-lightbox{display:none;position:fixed;top:0;left:0;right:0;bottom:0;z-index:10001;background:rgba(0,0,0,.85);cursor:zoom-out;align-items:center;justify-content:center}
      .img-lightbox.open{display:flex}
      .img-lightbox img{max-width:95vw;max-height:95vh;border-radius:4px;box-shadow:0 4px 24px rgba(0,0,0,.4)}
      /* CLS prevention: sidebar component styles (match main.css final state) */
      .sidebar-menu{margin:0;padding:0}
      .sidebar-tabs{display:flex;gap:0;margin:4px 0 0;border-bottom:1px solid #d8dce2}
      .sidebar-tab{flex:1;padding:9px 12px 8px;border:none;background:transparent;font:600 13px 'IBM Plex Sans',sans-serif;color:#757a87;cursor:pointer;border-bottom:2px solid transparent;margin-bottom:-1px;transition:color 0.15s,border-color 0.15s}
      .sidebar-tab.active{color:#1d3158;border-bottom-color:#1d3158}
      .sidebar-panel{display:none;padding-top:10px}
      .sidebar-panel.active{display:block}
      .sidebar-tools-list{margin:0;padding:0;list-style:none}
      .sidebar-tools-list li a{display:block;padding:5px 10px 5px 24px;font-size:14px;color:#495057;text-decoration:none;border-left:2px solid transparent;border-radius:0 4px 4px 0}
      .sidebar-section-header{padding:7px 12px;font-size:15px;font-weight:700;color:#212529;cursor:pointer;border-radius:4px}
      .sidebar-chevron{display:inline-block;font-size:10px;margin-right:4px;color:#757575}
      .sidebar-section-items{display:none;padding-left:0;margin:2px 0 6px}
      .sidebar-section.expanded .sidebar-section-items{display:block}
      .sidebar-section-items li{line-height:1.5}
      .sidebar-section-items li a{display:block;padding:4px 10px 4px 32px;font-size:14px;color:#495057;text-decoration:none;border-left:2px solid transparent;border-radius:0 4px 4px 0}
      .sidebar-divider{margin:12px 0 2px;padding:0 12px 4px 24px;font-size:11px;font-weight:700;letter-spacing:0.06em;text-transform:uppercase;color:#9ca3af;border-bottom:1px solid #f0f2f5;list-style:none}
      .sidebar-divider:first-child{margin-top:4px}
      .progress-dot{display:inline-block;width:10px;height:10px;border-radius:50%;border:1.5px solid #d1d5db;margin-right:7px;vertical-align:middle;flex-shrink:0;position:relative}
      /* Empty progress-dot (no status class) reads as an unchecked todo /
         disabled radio next to every sidebar item — visual noise that doesn't
         belong in a nav. Reserve the layout slot but hide the circle until
         the item actually has progress. visibility:hidden (not display:none)
         keeps the width stable when state flips. */
      .progress-dot:not(.started):not(.visited):not(.completed){visibility:hidden}
      /* CLS prevention: TOC sidebar matches main.css final state */
      #toc-wrapper{position:sticky;top:20px;max-height:calc(100vh - 40px);overflow-y:auto;padding-left:14px;border-left:1px solid #e9ecef}
      .toc-title{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:0.8px;color:#6c757d;margin-bottom:10px;padding-bottom:0}
      #toc{margin:0;padding:0}
      #toc li{line-height:1.45;margin-bottom:1px}
      #toc li a{font-size:13.5px;color:#6c757d;text-decoration:none;display:block;padding:3px 0;border-left:2px solid transparent;padding-left:8px;margin-left:-15px}
      #toc li a.toc-active{color:#1d3158;font-weight:600;border-left-color:#1d3158}
      /* CLS prevention: engagement strip layout (matches engagement.css) */
      .engagement-header{display:flex;flex-wrap:wrap;align-items:center;gap:6px 10px;font-family:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;font-size:12px;color:#64748b;letter-spacing:0.01em;margin:0.4em 0 1em;min-height:22px}
      .engagement-header:empty{display:none}
      /* CLS prevention: progress bar space (matches engagement.css) */
      .engagement-progress{min-height:32px;margin:1.2em 0 1.6em}
      /* CLS prevention: WebR editor min-height so the static→textarea swap doesn't shift layout */
      .webr-editor{min-height:60px}
      /* CLS prevention: images in content always reserve aspect ratio */
      #content img{max-width:100%;height:auto}

      /* =====================================================
         LAYOUT V2 (opt-in via body.layout-v2). Retry 2026-05-29.
         Differences from the first attempt:
           1. Sidebar columns use clamp(180px, 16vw, 260px) so they
              SHRINK on narrow viewports (first attempt used minmax
              which pinned both sides at 260px, squeezing content on
              typical laptops to ~460px).
           2. Sidebar links get overflow-wrap so long tutorial titles
              don't escape the narrower column.
           3. min-width:0 on every grid child so they can shrink.
           4. Right TOC breakpoint raised from 1100px -> 1280px so it
              only shows when the viewport can actually afford it.
           5. The inline-code background restyle is dropped - kept
              current syntax-highlighter behavior.
         All rules scoped under body.layout-v2 so pages without it
         render identically.
         ===================================================== */
      body.layout-v2{
        --lv2-bg:#f8f9fb;--lv2-card:#fff;--lv2-ink:#0d1117;
        --lv2-mut:#4b5260;--lv2-faint:#5b6573;
        --lv2-navy:#1c2c4f;--lv2-navy-h:#2d4173;--lv2-navy-soft:#eef1f7;
        --lv2-accent:#2056d2;--lv2-accent-soft:#e9efff;
        --lv2-line:#e4e7ee;--lv2-border:#d4d9e3;
        --lv2-green:#15803d;
        background:var(--lv2-bg);color:var(--lv2-ink);
      }
      html.dark body.layout-v2{
        --lv2-bg:#0a0f1c;--lv2-card:#0f1525;--lv2-ink:#eef2fa;
        --lv2-mut:#a5afc4;--lv2-faint:#9aa6c0;
        --lv2-navy:#5170b3;--lv2-navy-h:#6587c4;--lv2-navy-soft:#192240;
        --lv2-accent:#7faaff;--lv2-accent-soft:#1a2748;
        --lv2-line:#1f2a48;--lv2-border:#2c3a62;
      }

      /* Wider container; clamp-based grid that scales with viewport.
         width:auto is REQUIRED because the base critical CSS has
         @media(min-width:1200px){.container{width:1170px}} which would
         otherwise pin width to 1170 and ignore max-width:1340. */
      body.layout-v2 .container{max-width:1340px;width:auto;padding:0 22px}
      body.layout-v2 .site-masthead-inner{max-width:1340px}
      /* The legacy .site-masthead has margin:0 -15px to cancel the
         Bootstrap .container padding of 15px. Under layout-v2 the
         container padding is 22px, so the negative margin leaves a
         7px inset. Zero it so the masthead aligns flush with the
         article shell. */
      body.layout-v2 .site-masthead{margin-left:0;margin-right:0}
      body.layout-v2 .row{
        display:grid;
        grid-template-columns:
          clamp(180px, 16vw, 260px)
          minmax(0, 1fr)
          clamp(180px, 16vw, 260px);
        gap:0;margin-left:0;margin-right:0;
      }
      /* Bootstrap inserts .row::before AND .row::after pseudo-elements
         (content:" "; display:table) as a clearfix. Under display:grid
         these pseudos count as grid items. ::before grabs col 1, pushing
         every real child one column to the right and wrapping the last
         child to a new row. The 2026-05-29 first attempt only disabled
         ::after, resulting in nav in col 2, content in col 3, and toc
         wrapping to a new row at col 1 (the bug the user reported as
         "sidebar wide, content narrow"). BOTH pseudos must be killed. */
      body.layout-v2 .row::before,
      body.layout-v2 .row::after{display:none;content:none}
      /* min-width:0 lets grid children shrink below their content's
         intrinsic min-width; without this, long unbreakable text in any
         child forces the column wider than the grid template intended. */
      /* Drop Bootstrap's float and width on the legacy .col-sm-* hooks
         so the parent .row's CSS grid owns sizing. DO NOT zero horizontal
         padding here — per-column padding lives in the dedicated rules
         below (sidebar, main#content, #toc-sidebar) and gives the article
         the 44px breathing room the mock has. */
      body.layout-v2 #nav.col-sm-3,
      body.layout-v2 main#content.col-sm-7,
      body.layout-v2 #toc-sidebar.col-sm-2{
        width:auto!important;float:none!important;
        min-width:0;min-height:0;
      }
      body.layout-v2 #nav.col-sm-3{
        padding:14px 10px 40px;border-right:1px solid var(--lv2-line);
        position:sticky;top:60px;height:calc(100vh - 60px);overflow-y:auto;
      }
      /* Inner #sidebar-nav had its own sticky + overflow from the legacy critical
         CSS; under layout-v2 the outer #nav owns scrolling, so flatten the inner
         one to avoid a double scrollbar. */
      body.layout-v2 #sidebar-nav{
        position:static;max-height:none;overflow:visible;padding:0;
      }
      /* Wrap long tutorial titles in the sidebar so they never overflow */
      body.layout-v2 #nav a,
      body.layout-v2 #nav span,
      body.layout-v2 #sidebar-nav a,
      body.layout-v2 #sidebar-nav li{
        overflow-wrap:break-word;word-break:break-word;
      }
      body.layout-v2 main#content{padding:24px 44px 60px}

      /* S3 — Code-block bottom spacing.
         Default .webr-container margin is 22/22; the dark block visually
         carries a lot of weight, so the next paragraph reads as cramped.
         Lift bottom to 30px under layout-v2. */
      body.layout-v2 #content .webr-container{margin-bottom:30px}

      /* S7 — Further Reading: convert auto-injected <ul> to a 2-column
         card grid that matches the .rt-grid pattern used elsewhere.
         No HTML/auto_link.py changes needed — pure CSS. */
      body.layout-v2 #content #auto-further-reading .further-reading-list{
        list-style:none;padding:0;margin:14px 0 0;
        display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;
      }
      body.layout-v2 #content #auto-further-reading .further-reading-list li{margin:0}
      body.layout-v2 #content #auto-further-reading .further-reading-list li a{
        display:block;padding:14px 16px;
        background:var(--lv2-card);border:1px solid var(--lv2-border);
        border-radius:8px;color:var(--lv2-ink);
        font-weight:500;font-size:15px;line-height:1.4;
        text-decoration:none;
        transition:border-color .15s,background .15s,transform .15s;
      }
      body.layout-v2 #content #auto-further-reading .further-reading-list li a:hover{
        border-color:var(--lv2-accent);background:var(--lv2-accent-soft);
        text-decoration:none;transform:translateY(-1px);
      }
      @media(max-width:820px){
        body.layout-v2 #content #auto-further-reading .further-reading-list{
          grid-template-columns:1fr;
        }
      }
      body.layout-v2 #toc-sidebar{padding:24px 18px;position:sticky;top:74px;align-self:start}
      @media(max-width:1280px){
        body.layout-v2 .row{grid-template-columns:clamp(180px, 18vw, 260px) minmax(0,1fr)}
        body.layout-v2 #toc-sidebar{display:none}
      }
      @media(max-width:820px){
        body.layout-v2 .row{grid-template-columns:1fr}
        body.layout-v2 #nav{display:none}
        body.layout-v2 main#content{padding:20px}
      }

      /* Typography refresh - sized to mock spec */
      body.layout-v2 #content{
        font-size:16.5px;line-height:1.7;color:var(--lv2-ink);
        font-feature-settings:"tnum","ss01","cv11";text-rendering:optimizeLegibility;
      }
      body.layout-v2 #content p{line-height:1.7;margin:13px 0;color:var(--lv2-ink);text-wrap:pretty}
      body.layout-v2 #content h1{
        font-size:38px;font-weight:700;line-height:1.2;letter-spacing:-0.018em;
        margin:10px 0 13px;text-wrap:balance;color:var(--lv2-ink);
      }
      /* H2: hairline divider + breathing room above. Mock breaks each
         section with a top rule and ~48px space; staging used 34px and no
         divider, leaving sections to blur together. :first-of-type keeps
         the very first H2 flush with the actionbar (no double divider). */
      body.layout-v2 #content h2{
        font-size:25px;font-weight:600;line-height:1.25;letter-spacing:-0.018em;
        margin:48px 0 12px;padding-top:32px;border-top:1px solid var(--lv2-line);
        text-wrap:balance;color:var(--lv2-ink);
      }
      body.layout-v2 #content h2:first-of-type{
        margin-top:24px;padding-top:0;border-top:none;
      }
      body.layout-v2 #content h3,body.layout-v2 #content h4{
        font-size:18px;font-weight:600;line-height:1.3;margin:24px 0 8px;text-wrap:balance;color:var(--lv2-ink);
      }
      /* Specificity bump: `body.layout-v2 #content p` (1 id + 1 class
         + 2 elements) was beating `body.layout-v2 p.lead` (2 classes +
         2 elements) and forcing the dek to var(--lv2-ink) instead of
         var(--lv2-mut). Adding #content here matches that specificity. */
      body.layout-v2 #content p.lead{
        font-size:18.5px;line-height:1.6;color:var(--lv2-mut);
        border-left:3px solid var(--lv2-navy);padding-left:17px;margin:-2px 0 20px;font-weight:400;
      }

      /* Body link color: legacy a{color:#1d3158} and Bootstrap .text-muted
         leave inline links almost indistinguishable from body text. Use
         the mock accent so links are obviously clickable. Excludes
         buttons, cards, prev/next nav, and TOC items which have their
         own palette. */
      body.layout-v2 #content a:not(.btn):not(.rt-card):not(.pn-link):not(.lv2-anchor):not([class*="toc"]){
        color:var(--lv2-accent);
      }
      body.layout-v2 #content a:not(.btn):not(.rt-card):not(.pn-link):not(.lv2-anchor):not([class*="toc"]):hover{
        text-decoration:underline;
      }

      /* Inline <code> palette: match the mock's navy-soft tint instead
         of the legacy purple-blue (#eef vs #eef1f7). */
      body.layout-v2 #content :not(pre) > code{
        background:var(--lv2-navy-soft);color:var(--lv2-ink);
        border-radius:4px;padding:2px 5px;font-size:0.92em;
      }

      /* TOC right rail */
      body.layout-v2 #toc-sidebar .toc-title{font-size:10.5px;font-weight:700;text-transform:uppercase;letter-spacing:.08em;color:var(--lv2-faint);margin-bottom:9px}
      body.layout-v2 #toc{font-size:13px}
      body.layout-v2 #toc li{margin:0;line-height:1.45}
      body.layout-v2 #toc li a{
        display:block;padding:5px 0 5px 11px;
        border-left:2px solid var(--lv2-line);
        color:var(--lv2-faint);font-size:13px;
        transition:color .15s,border-color .15s;
      }
      body.layout-v2 #toc li a:hover{color:var(--lv2-ink)}
      body.layout-v2 #toc li a.toc-active{
        border-left-color:var(--lv2-navy);color:var(--lv2-ink);font-weight:600;
      }

      /* Reading progress bar - uses transform:scaleX so we don't fight any
         containing-block / overflow quirks that can pin a width-% bar to 0. */
      .lv2-progress{
        position:fixed;top:0;left:0;width:100vw;height:3px;
        background:var(--lv2-accent,#2056d2);z-index:90;
        transform:scaleX(0);transform-origin:left center;
        transition:transform .1s ease-out;pointer-events:none;
      }

      /* Heading anchor links (hover-reveal) */
      body.layout-v2 #content h2,
      body.layout-v2 #content h3,
      body.layout-v2 #content h4{position:relative}
      body.layout-v2 .lv2-anchor{
        position:absolute;left:-26px;top:50%;transform:translateY(-50%);
        font-size:.55em;color:var(--lv2-faint);text-decoration:none;
        opacity:0;transition:opacity .15s,color .15s;
        cursor:pointer;padding:4px 6px;line-height:1;font-weight:400;
      }
      body.layout-v2 #content h2:hover .lv2-anchor,
      body.layout-v2 #content h3:hover .lv2-anchor,
      body.layout-v2 #content h4:hover .lv2-anchor,
      body.layout-v2 .lv2-anchor:focus-visible{opacity:1}
      body.layout-v2 .lv2-anchor:hover{color:var(--lv2-accent)}
      @media(max-width:820px){body.layout-v2 .lv2-anchor{left:0;top:-22px;transform:none}}

      /* Focus ring refresh */
      body.layout-v2 a:focus-visible,
      body.layout-v2 button:focus-visible,
      body.layout-v2 input:focus-visible,
      body.layout-v2 textarea:focus-visible{
        outline:none;
        box-shadow:0 0 0 3px rgba(32,86,210,.22);
        border-radius:4px;
      }
      html.dark body.layout-v2 a:focus-visible,
      html.dark body.layout-v2 button:focus-visible,
      html.dark body.layout-v2 input:focus-visible{box-shadow:0 0 0 3px rgba(127,170,255,.22)}

      /* Reduced motion: shut everything down for users who request it */
      @media (prefers-reduced-motion: reduce){
        body.layout-v2 *,body.layout-v2 *::before,body.layout-v2 *::after{
          animation-duration:0.01ms!important;
          animation-iteration-count:1!important;
          transition-duration:0.01ms!important;
          scroll-behavior:auto!important;
        }
      }
    </style>
    <!-- Full Bootstrap deferred (non-render-blocking) -->
    <link href="www/bootstrap.min.css?h=dae0a568" rel="stylesheet" media="print" onload="this.media='all'">
    <noscript><link href="www/bootstrap.min.css?h=dae0a568" rel="stylesheet"></noscript>
    <link href="www/highlight.min.css?h=f103014a" rel="stylesheet" media="print" onload="this.media='all'">
    <link href="css/main.min.css?h=026681ec" rel="stylesheet" media="print" onload="this.media='all'">
    <noscript><link href="css/main.min.css?h=026681ec" rel="stylesheet"></noscript>
    <style>
      a{color:#1d3158}a:hover{text-decoration:underline}
      li{line-height:1.65}
      .MathJax_Display{margin:0}
      blockquote p{line-height:1.75;color:#717171}
      /* engagement.js renders a meta strip into .engagement-header that
         duplicates the byline (difficulty + time). Hide it; saved-posts-
         button.js reads the data-* attrs directly for the byline. */
      .engagement-header{display:none!important}
      /* Byline (saved-posts widget rebuilds this after H1+lead, mock-style) */
      .byline{display:flex;flex-wrap:wrap;align-items:center;gap:8px;
        font-size:13.5px;color:#4b5260;margin:6px 0 16px;line-height:1.5}
      /* P1 — bump avatar 26→30 to match mock visual weight. */
      .byline .av-sm{width:30px;height:30px;border-radius:50%;
        background:linear-gradient(135deg,#1c2c4f,#2d4173);color:#fff;
        display:inline-flex;align-items:center;justify-content:center;
        font-weight:700;font-size:12px;flex:none;letter-spacing:.02em}
      .byline .who{color:#0d1117;font-weight:600}
      .byline .dot{color:#c0c5cf}
      .byline .rev{color:#137a3e;font-weight:600;display:inline-flex;align-items:center;gap:4px}
      .byline .time{display:inline-flex;align-items:center;gap:4px;color:#6b7280}
      .byline .diff{font-size:10.5px;font-weight:700;text-transform:uppercase;
        letter-spacing:.05em;background:#eef1f7;color:#4b5260;
        padding:3px 8px;border-radius:999px;margin-left:2px}

      /* Action bar (saved-posts widget injects this after byline) */
      .actionbar{display:flex;align-items:center;gap:9px;margin:10px 0 26px;padding:12px 0;
        border-top:1px solid #e4e7ee;border-bottom:1px solid #e4e7ee;flex-wrap:wrap}
      .actionbar .act{display:inline-flex;align-items:center;gap:6px;border:1px solid #d4d9e3;
        background:#fff;border-radius:9px;padding:7px 12px;font-size:13px;font-weight:600;
        color:#4b5260;cursor:pointer;font-family:inherit;
        transition:border-color .15s,color .15s,background .15s}
      .actionbar .act:hover{border-color:#0a0d14;color:#0a0d14}
      .actionbar .act.bookmark-btn[data-saved="1"]{background:#fef3c7;border-color:#f59e0b;color:#92400e}
      .actionbar .act.bookmark-btn[data-saved="1"] svg{fill:#f59e0b}
      .actionbar .act:disabled{opacity:.55;cursor:wait}
      .actionbar-sync{margin-left:auto;font-size:12px;color:#6b7280}
      .actionbar-sync a{color:#2056d2;font-weight:600;text-decoration:none}
      .actionbar-sync a:hover{text-decoration:underline}

      /* Dark-mode overrides for byline + actionbar. The hard-coded #0d1117
         on .who renders invisible on the dark background; the action-bar
         borders and surfaces also need to flip. Tokens (--lv2-ink, --lv2-mut,
         --lv2-line, --lv2-card) already swap under html.dark body.layout-v2;
         we just need to point the hard-coded rules at them under dark. */
      html.dark body.layout-v2 .byline{color:var(--lv2-mut)}
      html.dark body.layout-v2 .byline .who{color:var(--lv2-ink)}
      html.dark body.layout-v2 .byline .dot{color:var(--lv2-faint)}
      html.dark body.layout-v2 .byline .time{color:var(--lv2-mut)}
      html.dark body.layout-v2 .byline .diff{background:var(--lv2-navy-soft);color:var(--lv2-mut)}
      html.dark body.layout-v2 .actionbar{border-top-color:var(--lv2-line);border-bottom-color:var(--lv2-line)}
      html.dark body.layout-v2 .actionbar .act{background:var(--lv2-card);border-color:var(--lv2-border);color:var(--lv2-mut)}
      html.dark body.layout-v2 .actionbar .act:hover{border-color:var(--lv2-ink);color:var(--lv2-ink)}
      html.dark body.layout-v2 .actionbar-sync{color:var(--lv2-mut)}

      /* Toast (Share button "Link copied" feedback) */
      .rs-toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%) translateY(8px);
        background:#0a0d14;color:#fff;padding:9px 18px;border-radius:8px;font-size:13px;
        font-family:'IBM Plex Sans',sans-serif;z-index:1000;opacity:0;pointer-events:none;
        transition:opacity .2s,transform .2s;box-shadow:0 8px 24px rgba(10,13,20,.25)}
      .rs-toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
      /* Auth-state visibility helpers (used by masthead variants) */
      .auth-anon,.auth-user{display:none}
      body.state-anon .auth-anon{display:inline-flex;align-items:center}
      body.state-pro .auth-user{display:inline-flex;align-items:center;gap:8px}
      .masthead-auth-link{font-family:'IBM Plex Sans',sans-serif;color:#4a5160;font-size:13.5px;font-weight:500;padding:6px 10px;border-radius:6px;text-decoration:none;transition:background .15s,color .15s;max-width:160px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
      .masthead-auth-link:hover{background:#f1f3f6;color:#0d1117;text-decoration:none}
      html.dark .masthead-auth-link{color:#c3cad9}
      html.dark .masthead-auth-link:hover{background:#1f242c;color:#fff}
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href="/ggplot2-Aesthetics-aes-Map-Data.html"><span class="progress-dot"></span>ggplot2 Aesthetics (aes)</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Colours.html"><span class="progress-dot"></span>ggplot2 Colours</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Scales.html"><span class="progress-dot"></span>ggplot2 Scales</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Themes-in-R.html"><span class="progress-dot"></span>ggplot2 Themes</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Labels-and-Annotations.html"><span class="progress-dot"></span>Labels &amp; Annotations</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Facets.html"><span class="progress-dot"></span>ggplot2 Facets</a></li><li data-subkey="sec2sub1"><a href="/ggplot2-Exercises-in-R-quiz.html"><span class="progress-dot"></span>ggplot2 Quiz</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub2" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Core Charts</li><li data-subkey="sec2sub2"><a href="/ggplot2-Scatter-Plots.html"><span class="progress-dot"></span>Scatter Plots</a></li><li data-subkey="sec2sub2"><a href="/ggplot2-Line-Charts.html"><span class="progress-dot"></span>Line Charts</a></li><li data-subkey="sec2sub2"><a href="/ggplot2-Bar-Charts.html"><span class="progress-dot"></span>Bar Charts</a></li><li data-subkey="sec2sub2"><a href="/ggplot2-Distribution-Charts.html"><span class="progress-dot"></span>Distribution Charts</a></li><li data-subkey="sec2sub2"><a href="/Error-Bars-in-R.html"><span class="progress-dot"></span>Error Bars</a></li><li data-subkey="sec2sub2"><a href="/geom_smooth-in-R.html"><span class="progress-dot"></span>geom_smooth()</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub3" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Distributions &amp; Groups</li><li data-subkey="sec2sub3"><a href="/Violin-Plot-in-R.html"><span class="progress-dot"></span>Violin Plot</a></li><li data-subkey="sec2sub3"><a href="/Ridgeline-Plot-in-R.html"><span class="progress-dot"></span>Ridgeline Plot</a></li><li data-subkey="sec2sub3"><a href="/Lollipop-Chart-in-R.html"><span class="progress-dot"></span>Lollipop Chart</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub4" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Relationships</li><li data-subkey="sec2sub4"><a href="/Bubble-Chart-in-R.html"><span class="progress-dot"></span>Bubble Chart</a></li><li data-subkey="sec2sub4"><a href="/Heatmap-in-R.html"><span class="progress-dot"></span>Heatmap in R</a></li><li data-subkey="sec2sub4"><a href="/Correlation-Matrix-Plot-in-R.html"><span class="progress-dot"></span>Correlation Matrix</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub5" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Advanced Charts</li><li data-subkey="sec2sub5"><a href="/Pie-Donut-Chart-in-R.html"><span class="progress-dot"></span>Pie &amp; Donut Chart</a></li><li data-subkey="sec2sub5"><a href="/Treemap-in-R.html"><span class="progress-dot"></span>Treemap</a></li><li data-subkey="sec2sub5"><a href="/Waffle-Chart-in-R.html"><span class="progress-dot"></span>Waffle Chart</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub6" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Exploratory Analysis</li><li data-subkey="sec2sub6"><a href="/Exploratory-Data-Analysis-in-R.html"><span class="progress-dot"></span>EDA (7-Step Framework)</a></li><li data-subkey="sec2sub6"><a href="/Univariate-EDA-in-R.html"><span class="progress-dot"></span>Univariate EDA</a></li><li data-subkey="sec2sub6"><a href="/Bivariate-EDA-in-R.html"><span class="progress-dot"></span>Bivariate EDA</a></li><li data-subkey="sec2sub6"><a href="/Descriptive-Statistics-in-R.html"><span class="progress-dot"></span>Descriptive Statistics</a></li><li data-subkey="sec2sub6"><a href="/Correlation-Analysis-in-R.html"><span class="progress-dot"></span>Correlation Analysis</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub7" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Interactive &amp; Maps</li><li data-subkey="sec2sub7"><a href="/Combining-ggplot2-with-plotly.html"><span class="progress-dot"></span>ggplot2 + plotly Interactive</a></li><li data-subkey="sec2sub7"><a href="/Interactive-Maps-in-R-with-leaflet.html"><span class="progress-dot"></span>Leaflet Interactive Maps</a></li><li data-subkey="sec2sub7"><a href="/Spatial-Data-in-R-with-sf.html"><span class="progress-dot"></span>Spatial Data (sf)</a></li><li data-subkey="sec2sub7"><a href="/Choropleth-Maps-in-R.html"><span class="progress-dot"></span>Choropleth Maps (sf)</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec2sub8" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Customization &amp; Reference</li><li data-subkey="sec2sub8"><a href="/ggplot2-Legends-in-R.html"><span class="progress-dot"></span>ggplot2 Legends</a></li><li data-subkey="sec2sub8"><a href="/ggplot2-Secondary-Axis.html"><span class="progress-dot"></span>Secondary Axis</a></li><li data-subkey="sec2sub8"><a href="/ggplot2-Log-Scale.html"><span class="progress-dot"></span>Log Scale</a></li><li data-subkey="sec2sub8"><a href="/patchwork-Package.html"><span class="progress-dot"></span>patchwork (Combine Plots)</a></li><li data-subkey="sec2sub8"><a href="/Publication-Quality-Figures-in-R.html"><span class="progress-dot"></span>Publication-Ready Figures</a></li><li data-subkey="sec2sub8"><a href="/ggplot2-cheatsheet.html"><span class="progress-dot"></span>ggplot2 Quickref</a></li><li data-subkey="sec2sub8"><a href="/Advanced-ggplot2-Course.html"><span class="progress-dot"></span>Advanced ggplot2 (Course)</a></li><li data-subkey="sec2sub8"><a href="/ggplot2-Course.html"><span class="progress-dot"></span>ggplot2 (Course)</a></li><li data-subkey="sec2sub8"><a href="/Dashboards-Course.html"><span class="progress-dot"></span>Interactive Dashboards (Course)</a></li></ul></li><li class="sidebar-section"><div class="sidebar-section-header"><span class="sidebar-chevron">&#9656;</span> Statistics<span class="section-meta" data-section-meta></span></div><ul class="sidebar-section-items list-unstyled"><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec3sub1" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> EDA &amp; Data Quality</li><li data-subkey="sec3sub1"><a href="/Automated-EDA-in-R.html"><span class="progress-dot"></span>Automated EDA</a></li><li data-subkey="sec3sub1"><a href="/Missing-Data-Visualization-in-R-naniar.html"><span class="progress-dot"></span>Missing Data Viz (naniar)</a></li><li data-subkey="sec3sub1"><a href="/Outlier-Detection-in-R.html"><span class="progress-dot"></span>Outlier Detection</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec3sub2" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Probability</li><li data-subkey="sec3sub2"><a href="/Sample-Spaces-Events-and-Probability-Axioms-in-R-With-Monte-Carlo-Proof.html"><span class="progress-dot"></span>Probability Axioms</a></li><li data-subkey="sec3sub2"><a href="/Conditional-Probability-in-R.html"><span class="progress-dot"></span>Conditional Probability</a></li><li data-subkey="sec3sub2"><a href="/Random-Variables-in-R.html"><span class="progress-dot"></span>Random Variables</a></li><li data-subkey="sec3sub2"><a href="/Binomial-and-Poisson-Distributions-in-R.html"><span class="progress-dot"></span>Binomial vs Poisson</a></li><li data-subkey="sec3sub2"><a href="/Normal-t-F-and-Chi-Squared-Distributions-in-R.html"><span class="progress-dot"></span>Normal, t, F, Chi-Squared</a></li><li data-subkey="sec3sub2"><a href="/Central-Limit-Theorem-in-R.html"><span class="progress-dot"></span>Central Limit Theorem</a></li><li data-subkey="sec3sub2"><a href="/Sampling-Distributions-in-R.html"><span class="progress-dot"></span>Sampling Distributions</a></li><li data-subkey="sec3sub2"><a href="/Law-of-Large-Numbers-vs-CLT-in-R.html"><span class="progress-dot"></span>LLN vs CLT</a></li><li data-subkey="sec3sub2"><a href="/What-Is-Probability-Simulation-First-Intuition-in-R-Before-the-Formulas.html"><span class="progress-dot"></span>Probability (Simulation-First)</a></li><li data-subkey="sec3sub2"><a href="/Expected-Value-and-Variance-in-R.html"><span class="progress-dot"></span>Expected Value and Variance</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec3sub3" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Inference &amp; Estimation</li><li data-subkey="sec3sub3"><a href="/Maximum-Likelihood-Estimation-in-R.html"><span class="progress-dot"></span>Maximum Likelihood Estimation</a></li><li data-subkey="sec3sub3"><a href="/Hypothesis-Testing-in-R.html"><span class="progress-dot"></span>Hypothesis Testing</a></li><li data-subkey="sec3sub3"><a href="/Sample-Size-Planning-in-R.html"><span class="progress-dot"></span>Sample Size Planning</a></li><li data-subkey="sec3sub3"><a href="/Which-Statistical-Test-in-R.html"><span class="progress-dot"></span>Choosing the Right Test</a></li><li data-subkey="sec3sub3"><a href="/Statistical-Tests-in-R.html"><span class="progress-dot"></span>Statistical Tests</a></li><li data-subkey="sec3sub3"><a href="/Measures-of-Association-in-R.html"><span class="progress-dot"></span>Measures of Association</a></li><li data-subkey="sec3sub3"><a href="/Point-Estimation-in-R.html"><span class="progress-dot"></span>Point Estimation</a></li><li data-subkey="sec3sub3"><a href="/Confidence-Intervals-in-R.html"><span class="progress-dot"></span>Confidence Intervals</a></li><li data-subkey="sec3sub3"><a href="/Type-I-and-Type-II-Errors-in-R.html"><span class="progress-dot"></span>Type I and II Errors</a></li><li data-subkey="sec3sub3"><a href="/Statistical-Power-Analysis-in-R.html"><span class="progress-dot"></span>Power Analysis</a></li><li data-subkey="sec3sub3"><a href="/Effect-Size-in-R.html"><span class="progress-dot"></span>Effect Size</a></li><li data-subkey="sec3sub3"><a href="/t-Tests-in-R.html"><span class="progress-dot"></span>t-Tests</a></li><li data-subkey="sec3sub3"><a href="/Proportion-Tests-in-R.html"><span class="progress-dot"></span>Proportion Tests</a></li><li data-subkey="sec3sub3"><a href="/Normality-and-Variance-Tests-in-R.html"><span class="progress-dot"></span>Normality &amp; Variance Tests</a></li><li data-subkey="sec3sub3"><a href="/Chi-Square-Tests-in-R.html"><span class="progress-dot"></span>Chi-Square Tests</a></li><li data-subkey="sec3sub3"><a href="/Wilcoxon-Mann-Whitney-and-Kruskal-Wallis-in-R.html"><span class="progress-dot"></span>Wilcoxon, Mann-Whitney &amp; Kruskal-Wallis</a></li><li data-subkey="sec3sub3"><a href="/Multiple-Comparisons-in-R.html"><span class="progress-dot"></span>Multiple Testing Correction</a></li><li data-subkey="sec3sub3"><a href="/Hypothesis-Testing-Exercises-in-R-quiz.html"><span class="progress-dot"></span>Hypothesis Testing Quiz</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec3sub4" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Regression</li><li data-subkey="sec3sub4"><a href="/Linear-Regression.html"><span class="progress-dot"></span>Linear Regression</a></li><li data-subkey="sec3sub4"><a href="/Logistic-Regression-With-R.html"><span class="progress-dot"></span>Logistic Regression</a></li><li data-subkey="sec3sub4"><a href="/Variable-Selection-and-Importance-With-R.html"><span class="progress-dot"></span>Feature Selection</a></li><li data-subkey="sec3sub4"><a href="/Model-Selection-in-R.html"><span class="progress-dot"></span>Model Selection</a></li><li data-subkey="sec3sub4"><a href="/Missing-Value-Treatment-With-R.html"><span class="progress-dot"></span>Missing Value Treatment</a></li><li data-subkey="sec3sub4"><a href="/Outlier-Treatment-With-R.html"><span class="progress-dot"></span>Outlier Analysis</a></li><li data-subkey="sec3sub4"><a href="/adv-regression-models.html"><span class="progress-dot"></span>Advanced Regression Models</a></li><li data-subkey="sec3sub4"><a href="/Linear-Regression-Exercises-in-R-quiz.html"><span class="progress-dot"></span>Linear Regression Quiz</a></li><li class="sidebar-divider sidebar-subsection-toggle" data-subkey="sec3sub5" data-collapsed="false"><span class="subsec-chevron">&#9660;</span> Reporting</li><li data-subkey="sec3sub5"><a href="/Statistical-Consulting-in-R.html"><span class="progress-dot"></span>Statistical Consulting</a></li><li data-subkey="sec3sub5"><a href="/Statistical-Report-Writing-in-R.html"><span class="progress-dot"></span>Statistical Report Writing</a></li><li data-subkey="sec3sub5"><a href="/Bootstrap-Confidence-Intervals-in-R.html"><span class="progress-dot"></span>Bootstrap Confidence Intervals</a></li><li data-subkey="sec3sub5"><a href="/Reporting-Statistics-in-R.html"><span class="progress-dot"></span>Reporting Statistics</a></li><li data-subkey="sec3sub5"><a href="/Correlation-in-R.html"><span class="progress-dot"></span>Correlation (Pearson, Spearman, Kendall)</a></li><li data-subkey="sec3sub5"><a href="/Linear-Regression-Assumptions-in-R.html"><span class="progress-dot"></span>Linear Regression Assumptions</a></li><li data-subkey="sec3sub5"><a href="/Dummy-Variables-in-R.html"><span class="progress-dot"></span>Dummy Variables in R</a></li><li data-subkey="sec3sub5"><a href="/Interaction-Effects-in-R.html"><span class="progress-dot"></span>Interaction Effects</a></li><li data-subkey="sec3sub5"><a href="/Regression-Diagnostics-in-R.html"><span class="progress-dot"></span>Regression Diagnostics</a></li><li 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href="/Post-Hoc-Tests-After-ANOVA.html"><span class="progress-dot"></span>Post-Hoc Tests After ANOVA</a></li><li data-subkey="sec3sub5"><a href="/Two-Way-ANOVA-in-R.html"><span class="progress-dot"></span>Two-Way ANOVA</a></li><li data-subkey="sec3sub5"><a href="/Repeated-Measures-ANOVA-in-R.html"><span class="progress-dot"></span>Repeated Measures ANOVA</a></li><li data-subkey="sec3sub5"><a href="/ANCOVA-in-R.html"><span class="progress-dot"></span>ANCOVA</a></li><li data-subkey="sec3sub5"><a href="/Experimental-Design-Principles-in-R.html"><span class="progress-dot"></span>Experimental Design in R</a></li><li data-subkey="sec3sub5"><a href="/Factorial-Experiments-in-R.html"><span class="progress-dot"></span>Factorial Designs (2^k)</a></li><li data-subkey="sec3sub5"><a href="/AB-Testing-in-R.html"><span class="progress-dot"></span>A/B Testing</a></li><li data-subkey="sec3sub5"><a href="/MANOVA-in-R.html"><span class="progress-dot"></span>MANOVA</a></li><li data-subkey="sec3sub5"><a href="/Mixed-ANOVA-in-R.html"><span class="progress-dot"></span>Mixed ANOVA</a></li><li data-subkey="sec3sub5"><a href="/Multivariate-Statistics-in-R.html"><span class="progress-dot"></span>Multivariate Distances &amp; Hotelling's T²</a></li><li data-subkey="sec3sub5"><a href="/PCA-in-R.html"><span class="progress-dot"></span>PCA with prcomp()</a></li><li data-subkey="sec3sub5"><a href="/Interpreting-PCA-Results-in-R.html"><span class="progress-dot"></span>Interpreting PCA Output</a></li><li data-subkey="sec3sub5"><a href="/Exploratory-Factor-Analysis-in-R.html"><span class="progress-dot"></span>Exploratory Factor Analysis</a></li><li data-subkey="sec3sub5"><a href="/CFA-and-Structural-Equation-Modeling-in-R.html"><span class="progress-dot"></span>SEM and CFA (lavaan)</a></li><li data-subkey="sec3sub5"><a href="/Linear-Discriminant-Analysis-in-R.html"><span class="progress-dot"></span>LDA (Linear Discriminant Analysis)</a></li><li data-subkey="sec3sub5"><a href="/Cluster-Analysis-in-R.html"><span class="progress-dot"></span>Clustering (k-Means / HC / DBSCAN)</a></li><li data-subkey="sec3sub5"><a href="/Correspondence-Analysis-in-R.html"><span class="progress-dot"></span>Correspondence Analysis</a></li><li data-subkey="sec3sub5"><a href="/t-SNE-and-UMAP-in-R.html"><span class="progress-dot"></span>t-SNE and UMAP</a></li><li data-subkey="sec3sub5"><a href="/Simple-Linear-Regression-in-R.html"><span class="progress-dot"></span>Simple Linear Regression</a></li><li data-subkey="sec3sub5"><a href="/Multiple-Regression-in-R.html"><span class="progress-dot"></span>Multiple Regression</a></li><li data-subkey="sec3sub5"><a href="/Robust-Regression-in-R.html"><span class="progress-dot"></span>Robust Regression (rlm)</a></li><li data-subkey="sec3sub5"><a href="/factoextra-and-FactoMineR.html"><span class="progress-dot"></span>factoextra (PCA + Clusters)</a></li><li data-subkey="sec3sub5"><a href="/Categorical-Data-in-R.html"><span class="progress-dot"></span>Categorical Data (Tables &amp; Mosaic)</a></li><li data-subkey="sec3sub5"><a href="/Chi-Square-Test-of-Independence-in-R.html"><span class="progress-dot"></span>Chi-Square Test of Independence</a></li><li data-subkey="sec3sub5"><a href="/Chi-Square-Goodness-of-Fit-Test-in-R.html"><span class="progress-dot"></span>Chi-Square Goodness-of-Fit</a></li><li data-subkey="sec3sub5"><a href="/Fishers-Exact-Test-in-R.html"><span class="progress-dot"></span>Fisher's Exact Test</a></li><li data-subkey="sec3sub5"><a href="/Odds-Ratios-and-Relative-Risk-in-R.html"><span class="progress-dot"></span>Odds Ratios &amp; Relative Risk</a></li><li data-subkey="sec3sub5"><a href="/Logistic-Regression-in-R-2.html"><span class="progress-dot"></span>Logistic Regression (Diagnostics)</a></li><li data-subkey="sec3sub5"><a href="/Poisson-and-Negative-Binomial-Regression.html"><span class="progress-dot"></span>Poisson &amp; Negative Binomial Regression</a></li><li data-subkey="sec3sub5"><a href="/Multinomial-and-Ordinal-Logistic-Regression-in-R.html"><span class="progress-dot"></span>Multinomial &amp; Ordinal Logistic Regression</a></li><li data-subkey="sec3sub5"><a href="/When-to-Use-Nonparametric-Tests-in-R.html"><span class="progress-dot"></span>When to Use Nonparametric Tests</a></li><li data-subkey="sec3sub5"><a href="/Wilcoxon-Signed-Rank-Test-in-R.html"><span class="progress-dot"></span>Wilcoxon Signed-Rank Test</a></li><li data-subkey="sec3sub5"><a href="/Mann-Whitney-U-Test-in-R.html"><span class="progress-dot"></span>Mann-Whitney U Test</a></li><li data-subkey="sec3sub5"><a href="/Kruskal-Wallis-Test-in-R-2.html"><span class="progress-dot"></span>Kruskal-Wallis Test</a></li><li data-subkey="sec3sub5"><a href="/Friedman-Test-in-R.html"><span class="progress-dot"></span>Friedman Test</a></li><li data-subkey="sec3sub5"><a href="/Spearman-and-Kendall-Correlation-in-R.html"><span class="progress-dot"></span>Spearman &amp; Kendall Correlation</a></li><li data-subkey="sec3sub5"><a href="/Bootstrap-in-R.html"><span class="progress-dot"></span>Bootstrap (boot package)</a></li><li data-subkey="sec3sub5"><a href="/Quantile-Regression-in-R-2.html"><span class="progress-dot"></span>Quantile Regression</a></li><li data-subkey="sec3sub5"><a href="/Matrix-Operations-in-R.html"><span class="progress-dot"></span>Matrix Operations in R</a></li><li data-subkey="sec3sub5"><a href="/Solving-Linear-Systems-in-R.html"><span class="progress-dot"></span>Solving Linear Systems in R</a></li><li data-subkey="sec3sub5"><a href="/Eigenvalues-and-Eigenvectors-in-R.html"><span class="progress-dot"></span>Eigenvalues &amp; Eigenvectors in R</a></li><li data-subkey="sec3sub5"><a href="/Singular-Value-Decomposition-in-R.html"><span class="progress-dot"></span>Singular Value Decomposition in R</a></li><li data-subkey="sec3sub5"><a href="/Projections-and-the-Hat-Matrix-in-R.html"><span class="progress-dot"></span>Projections &amp; the Hat 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          <nav class="breadcrumb-nav" aria-label="Breadcrumb"><a href="/">Home</a> <span class="breadcrumb-sep">&rsaquo;</span> <span>Practice Exercises</span> <span class="breadcrumb-sep">&rsaquo;</span> <span class="breadcrumb-current">API Calls Exercises in R: 17 Real-World Practice Problems</span></nav>
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<h1>API Calls Exercises in R: 17 Real-World Practice Problems</h1>

<p class="lead">Seventeen practice problems on calling REST APIs from R with httr2 and <a class="auto-link" href="Importing-Data-in-R.html" title="Importing Data into R: read_csv(), read_excel(), read_json() — Complete Guide">jsonlite</a>: building requests, parsing JSON, handling auth, retries, rate limits, and pagination. Solutions are hidden so you can attempt each one cold and reveal only when stuck.</p>
<div class="post-byline" style="color:#6b7280;font-size:14px;margin:2px 0 18px 0;line-height:1.5;">By <strong>Selva Prabhakaran</strong> &nbsp;&middot;&nbsp; Published June 30, 2026 &nbsp;&middot;&nbsp; Last updated June 30, 2026</div>

<div class="engagement-header" data-difficulty="Mixed" data-time="40" data-exercises="17" data-xp="255"></div>

<pre><code class="language-r">library(httr2)
library(jsonlite)
library(dplyr)
library(tibble)
library(purrr)</code></pre>

<blockquote><p>The network exercises target public stable endpoints (<code>jsonplaceholder.typicode.com</code>, <code>httpbin.org</code>, <code>api.agify.io</code>). They are read-only sandboxes and safe to hit repeatedly. The auth and retry exercises use <code>req_dry_run()</code> so you can verify the wire request without sending it.</p></blockquote>

<h2>Section 1. Building and inspecting httr2 requests (4 problems)</h2>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-1-1" data-grade-mode="output-compare" data-difficulty="beginner">

<h3 class="exercise-title">Exercise 1.1: Construct a basic GET request and inspect its URL</h3>

<p class="exercise-task"><strong>Task:</strong> A junior analyst onboarding to the data team is exploring <code>httr2</code> for the first time. Build a request object pointing at <code>https://jsonplaceholder.typicode.com/posts/1</code> using <code>request()</code>, do NOT perform it, and save the request to <code>ex_1_1</code> so the analyst can examine the URL, method, and body before any traffic is sent.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; &lt;httr2_request&gt;
#&gt; GET https://jsonplaceholder.typicode.com/posts/1
#&gt; Body: empty</code></pre>
</div>

<p><strong>Difficulty:</strong> Beginner</p>

<div class="exercise-hints" hidden><p>A request in httr2 is a lazy description of a call - you state where to point it without sending anything over the network yet.</p><p>Pass the URL string to request() and assign the result to ex_1_1; do not add any perform step.</p></div>

<pre><code class="language-r">ex_1_1 &lt;- # your code here
ex_1_1</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">ex_1_1 &lt;- request(&quot;https://jsonplaceholder.typicode.com/posts/1&quot;)
ex_1_1
#&gt; &lt;httr2_request&gt;
#&gt; GET https://jsonplaceholder.typicode.com/posts/1
#&gt; Body: empty</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>request()</code> builds a lazy request object: no network traffic happens until you call <code>req_perform()</code> on it. This separation lets you <a class="auto-link" href="R-Function-Operators.html" title="R Function Operators: Compose, Negate & Partial Application">compose</a>, inspect, and unit-test requests safely. The printed representation shows method (default <code>GET</code>), URL, and body status, which is the fastest way to confirm you assembled the request correctly before sending it. The same object can be modified later with <code>req_url_path_append()</code> or <code>req_method()</code> rather than building a new request from scratch.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-1-2" data-grade-mode="output-compare" data-difficulty="beginner">

<h3 class="exercise-title">Exercise 1.2: Attach a custom User-Agent header</h3>

<p class="exercise-task"><strong>Task:</strong> Many APIs reject requests with a generic agent string. Take the request from Exercise 1.1, add a <code>User-Agent</code> header reading <code>r-statistics-tutorial/1.0 (selva@example.com)</code> with <code>req_user_agent()</code>, and save the modified request to <code>ex_1_2</code> so it identifies itself politely to the server.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; &lt;httr2_request&gt;
#&gt; GET https://jsonplaceholder.typicode.com/posts/1
#&gt; Headers:
#&gt; * User-Agent: 'r-statistics-tutorial/1.0 (selva@example.com)'
#&gt; Body: empty</code></pre>
</div>

<p><strong>Difficulty:</strong> Beginner</p>

<div class="exercise-hints" hidden><p>Identifying who is calling is just one more piece of metadata layered onto an existing request before it is sent.</p><p>Pipe the request from Exercise 1.1 into req_user_agent() with the agent string as its only argument.</p></div>

<pre><code class="language-r">ex_1_2 &lt;- # your code here
ex_1_2</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">ex_1_2 &lt;- request(&quot;https://jsonplaceholder.typicode.com/posts/1&quot;) |&gt;
  req_user_agent(&quot;r-statistics-tutorial/1.0 (selva@example.com)&quot;)
ex_1_2
#&gt; &lt;httr2_request&gt;
#&gt; GET https://jsonplaceholder.typicode.com/posts/1
#&gt; Headers:
#&gt; * User-Agent: 'r-statistics-tutorial/1.0 (selva@example.com)'
#&gt; Body: empty</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> A descriptive User-Agent is the polite-internet default: it tells the server who is calling so the operator can contact you if your script misbehaves. <code>req_user_agent()</code> is a thin wrapper around <code>req_headers()</code> that targets the User-Agent slot specifically, so subsequent <code>req_headers()</code> calls do not overwrite it accidentally. Generic agents like the default <code>httr2/x.y.z libcurl/...</code> are commonly throttled or 403'd by anti-bot middleware, so set this once at the top of your script.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-1-3" data-grade-mode="output-compare" data-difficulty="intermediate">

<h3 class="exercise-title">Exercise 1.3: Attach query parameters and dry-run the wire URL</h3>

<p class="exercise-task"><strong>Task:</strong> A data engineer needs to confirm that query parameters serialize correctly before pointing a job at production. Build a request to <code>https://api.agify.io</code>, add query parameters <code>name = &quot;selva&quot;</code> and <code>country_id = &quot;IN&quot;</code> with <code>req_url_query()</code>, then use <code>req_dry_run()</code> to print the wire-level request and save the unsent request to <code>ex_1_3</code>.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; GET /?name=selva&amp;country_id=IN HTTP/1.1
#&gt; host: api.agify.io
#&gt; user-agent: httr2/1.0.0 r-curl/5.2.0 libcurl/8.4.0
#&gt; accept: */*
#&gt; accept-encoding: deflate, gzip</code></pre>
</div>

<p><strong>Difficulty:</strong> Intermediate</p>

<div class="exercise-hints" hidden><p>Query parameters are key-value pairs appended to the URL, and the library can encode them for you instead of you hand-building the string.</p><p>Add req_url_query(name = "selva", country_id = "IN") to a request() for the base URL.</p></div>

<pre><code class="language-r">ex_1_3 &lt;- # your code here
ex_1_3 |&gt; req_dry_run()</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">ex_1_3 &lt;- request(&quot;https://api.agify.io&quot;) |&gt;
  req_url_query(name = &quot;selva&quot;, country_id = &quot;IN&quot;)

ex_1_3 |&gt; req_dry_run()
#&gt; GET /?name=selva&amp;country_id=IN HTTP/1.1
#&gt; host: api.agify.io
#&gt; user-agent: httr2/1.0.0 r-curl/5.2.0 libcurl/8.4.0
#&gt; accept: */*
#&gt; accept-encoding: deflate, gzip</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>req_url_query()</code> is preferable to hand-building a query string because it URL-encodes values for you (spaces, ampersands, unicode) and de-duplicates keys. <code>req_dry_run()</code> prints the exact HTTP message that would be sent without performing the request, which is invaluable when debugging mysterious 400 responses or auth failures. The header user-agent in your output may differ depending on installed <code>httr2</code> and <code>curl</code> versions; only the request line and host need to match.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-1-4" data-grade-mode="output-compare" data-difficulty="beginner">

<h3 class="exercise-title">Exercise 1.4: Switch a GET request to POST and inspect the body</h3>

<p class="exercise-task"><strong>Task:</strong> A code reviewer wants to see how the same request URL can be reused across HTTP methods. Take a request to <code>https://httpbin.org/anything</code>, change the method to <code>POST</code> with <code>req_method()</code>, attach a JSON body <code>list(team = &quot;data&quot;, priority = 1)</code> via <code>req_body_json()</code>, and save the unsent request to <code>ex_1_4</code> so the reviewer can inspect it before run-time.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; &lt;httr2_request&gt;
#&gt; POST https://httpbin.org/anything
#&gt; Body: json encoded data</code></pre>
</div>

<p><strong>Difficulty:</strong> Beginner</p>

<div class="exercise-hints" hidden><p>The same URL can carry a different verb and a payload - you reshape an existing request rather than build a new one.</p><p>Chain req_method("POST") and req_body_json(list(team = "data", priority = 1)) onto the request().</p></div>

<pre><code class="language-r">ex_1_4 &lt;- # your code here
ex_1_4</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">ex_1_4 &lt;- request(&quot;https://httpbin.org/anything&quot;) |&gt;
  req_method(&quot;POST&quot;) |&gt;
  req_body_json(list(team = &quot;data&quot;, priority = 1))
ex_1_4
#&gt; &lt;httr2_request&gt;
#&gt; POST https://httpbin.org/anything
#&gt; Body: json encoded data</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>req_body_json()</code> does two jobs at once: it serializes the R list to JSON with <code>jsonlite::toJSON()</code> AND sets the <code>Content-Type: application/json</code> header. If you skip the latter, many APIs will silently reject the body or treat it as form data. Note that calling <code>req_body_json()</code> also implicitly sets the method to <code>POST</code>, so the explicit <code>req_method(&quot;POST&quot;)</code> here is redundant but documentary. Use <code>req_dry_run()</code> to see the serialized JSON in the body.</p>

</details>

</section>

<h2>Section 2. Sending GET requests and parsing JSON (4 problems)</h2>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-2-1" data-grade-mode="output-compare" data-difficulty="intermediate">

<h3 class="exercise-title">Exercise 2.1: Fetch a JSON post and extract a single field</h3>

<p class="exercise-task"><strong>Task:</strong> A content team wants to pull the title of post 1 from a CMS-like sandbox. Perform a GET to <code>https://jsonplaceholder.typicode.com/posts/1</code>, parse the response with <code>resp_body_json()</code>, and save the value of the <code>title</code> element (a character scalar) to <code>ex_2_1</code> so it can be used in a downstream report.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; [1] &quot;sunt aut facere repellat provident occaecati excepturi optio reprehenderit&quot;</code></pre>
</div>

<p><strong>Difficulty:</strong> Intermediate</p>

<div class="exercise-hints" hidden><p>Sending the request returns a response, and the single value you want lives inside its parsed body.</p><p>After <a class="auto-link" href="REST-APIs-in-R-with-httr2.html" title="REST APIs in R with httr2: GET, POST, OAuth, and Paginated Results">req_perform()</a>, call resp_body_json() and pull the title element with $title.</p></div>

<pre><code class="language-r">ex_2_1 &lt;- # your code here
ex_2_1</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">resp &lt;- request(&quot;https://jsonplaceholder.typicode.com/posts/1&quot;) |&gt;
  req_perform()

parsed &lt;- resp |&gt; resp_body_json()
ex_2_1 &lt;- parsed$title
ex_2_1
#&gt; [1] &quot;sunt aut facere repellat provident occaecati excepturi optio reprehenderit&quot;</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>req_perform()</code> is the verb that finally sends bytes over the network and returns an <code>httr2_response</code> object. <code>resp_body_json()</code> parses the body as JSON using <code>jsonlite</code> under the hood and returns a nested R list (not a tibble) by default, because JSON is fundamentally heterogeneous. To get a data frame for arrays of records, pass <code>simplifyVector = TRUE</code> or use <code>jsonlite::fromJSON()</code> on <code>resp_body_string()</code>. Pulling a single field is just list extraction.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-2-2" data-grade-mode="self-check" data-difficulty="intermediate">

<h3 class="exercise-title">Exercise 2.2: Convert a list of JSON posts to a tidy tibble</h3>

<p class="exercise-task"><strong>Task:</strong> A reporting analyst needs every post by user 1 as a tibble for joining against an internal users table. Perform a GET to <code>https://jsonplaceholder.typicode.com/posts?userId=1</code>, parse the JSON array, and convert it to a tibble with columns <code>userId</code>, <code>id</code>, <code>title</code>, <code>body</code>. Save the result to <code>ex_2_2</code>.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; # A tibble: 10 x 4
#&gt;   userId    id title                                                       body
#&gt;    &lt;int&gt; &lt;int&gt; &lt;chr&gt;                                                       &lt;chr&gt;
#&gt; 1      1     1 sunt aut facere repellat provident occaecati excepturi opt~ quia~
#&gt; 2      1     2 qui est esse                                                est ~
#&gt; 3      1     3 ea molestias quasi exercitationem repellat qui ipsa sit au~ et i~
#&gt; ...
#&gt; # 7 more rows hidden</code></pre>
</div>

<p><strong>Difficulty:</strong> Intermediate</p>

<div class="exercise-hints" hidden><p>An array of flat JSON objects is already table-shaped - the work is getting it into a rectangular structure.</p><p>Take resp_body_string(), pass it to fromJSON(), then coerce with <a class="auto-link" href="tibble-as_tibble-in-R.html" title="tibble as_tibble() in R: Convert Objects to Tibbles">as_tibble()</a>.</p></div>

<pre><code class="language-r">ex_2_2 &lt;- # your code here
ex_2_2</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">resp &lt;- request(&quot;https://jsonplaceholder.typicode.com/posts&quot;) |&gt;
  req_url_query(userId = 1) |&gt;
  req_perform()

ex_2_2 &lt;- resp |&gt;
  resp_body_string() |&gt;
  fromJSON() |&gt;
  as_tibble()
ex_2_2
#&gt; # A tibble: 10 x 4
#&gt;   userId    id title                                                       body
#&gt;    &lt;int&gt; &lt;int&gt; &lt;chr&gt;                                                       &lt;chr&gt;
#&gt; 1      1     1 sunt aut facere repellat provident occaecati excepturi opt~ quia~
#&gt; 2      1     2 qui est esse                                                est ~
#&gt; ...</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>resp_body_json()</code> returns a list-of-lists for an array; <code>jsonlite::fromJSON()</code> on the raw string auto-simplifies a JSON array of flat objects into a data frame in one shot, which is usually what you want for "table-shaped" responses. If the records had nested objects (e.g., <code>address</code> with sub-fields), you would call <code>fromJSON(..., flatten = TRUE)</code> or use <code>tidyr::unnest_wider()</code> on the list-column. Always inspect with <code>glimpse()</code> before assuming column types.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-2-3" data-grade-mode="output-compare" data-difficulty="intermediate">

<h3 class="exercise-title">Exercise 2.3: Flatten a nested JSON response into a data frame</h3>

<p class="exercise-task"><strong>Task:</strong> A data team is reading a payload that contains user profiles with nested <code>address</code> and <code>company</code> objects. Parse the JSON string <code>nested_json</code> (defined below) with <code>fromJSON(flatten = TRUE)</code>, coerce to a tibble, and save only the columns <code>id</code>, <code>name</code>, <code>address.city</code>, <code>company.name</code> to <code>ex_2_3</code> for a quick directory view.</p>

<pre><code class="language-r">nested_json &lt;- '[
  {&quot;id&quot;:1,&quot;name&quot;:&quot;Leanne&quot;,&quot;address&quot;:{&quot;city&quot;:&quot;Gwenborough&quot;},&quot;company&quot;:{&quot;name&quot;:&quot;Romaguera-Crona&quot;}},
  {&quot;id&quot;:2,&quot;name&quot;:&quot;Ervin&quot;,  &quot;address&quot;:{&quot;city&quot;:&quot;Wisokyburgh&quot;}, &quot;company&quot;:{&quot;name&quot;:&quot;Deckow-Crist&quot;}},
  {&quot;id&quot;:3,&quot;name&quot;:&quot;Clementine&quot;,&quot;address&quot;:{&quot;city&quot;:&quot;McKenziehaven&quot;},&quot;company&quot;:{&quot;name&quot;:&quot;Romaguera-Jacobson&quot;}}
]'</code></pre>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; # A tibble: 3 x 4
#&gt;      id name        address.city  company.name
#&gt;   &lt;int&gt; &lt;chr&gt;       &lt;chr&gt;         &lt;chr&gt;
#&gt; 1     1 Leanne      Gwenborough   Romaguera-Crona
#&gt; 2     2 Ervin       Wisokyburgh   Deckow-Crist
#&gt; 3     3 Clementine  McKenziehaven Romaguera-Jacobson</code></pre>
</div>

<p><strong>Difficulty:</strong> Intermediate</p>

<div class="exercise-hints" hidden><p>Nested objects break the rectangle; collapsing them turns each sub-field into its own dotted column.</p><p>Call fromJSON() with flatten = TRUE, coerce with as_tibble(), then <a class="auto-link" href="dplyr-filter-select.html" title="dplyr filter() and select(): Subset Rows & Columns with Precision">select()</a> the four columns.</p></div>

<pre><code class="language-r">ex_2_3 &lt;- # your code here
ex_2_3</code></pre>

<details class="exercise-solution">
<summary>Click to reveal solution</summary>

<pre><code class="language-r">ex_2_3 &lt;- fromJSON(nested_json, flatten = TRUE) |&gt;
  as_tibble() |&gt;
  select(id, name, address.city, company.name)
ex_2_3
#&gt; # A tibble: 3 x 4
#&gt;      id name        address.city  company.name
#&gt;   &lt;int&gt; &lt;chr&gt;       &lt;chr&gt;         &lt;chr&gt;
#&gt; 1     1 Leanne      Gwenborough   Romaguera-Crona
#&gt; 2     2 Ervin       Wisokyburgh   Deckow-Crist
#&gt; 3     3 Clementine  McKenziehaven Romaguera-Jacobson</code></pre>

<p class="exercise-explanation"><strong>Explanation:</strong> <code>flatten = TRUE</code> collapses nested objects into dotted column names (<code>address.city</code>), which keeps the result rectangular and dplyr-friendly. Without <code>flatten</code>, you would get list-columns for <code>address</code> and <code>company</code> that need a second pass with <code>tidyr::unnest_wider()</code>. The dotted names contain periods, so wrap them in backticks if you need to reference them in <code>mutate()</code> or <code>filter()</code>. For deeply nested or irregular JSON, prefer <code>tibblify</code> or stepwise <code>unnest_*</code> over a single flat dump.</p>

</details>

</section>

<section class="exercise" data-exercise-id="API-Calls-Exercises-in-R-ex-2-4" data-grade-mode="output-compare" data-difficulty="beginner">

<h3 class="exercise-title">Exercise 2.4: Inspect status code, content type, and headers of a response</h3>

<p class="exercise-task"><strong>Task:</strong> A platform engineer reviewing log output wants a one-shot health check on an endpoint. Perform a GET to <code>https://jsonplaceholder.typicode.com/posts/1</code>, then build a <a class="auto-link" href="R-Lists.html" title="R Lists: When Data Frames Aren't Flexible Enough (Complete Guide)">named list</a> with elements <code>status</code> (from <code>resp_status()</code>), <code>content_type</code> (from <code>resp_content_type()</code>), and <code>server</code> (the <code>server</code> response header via <code>resp_header()</code>). Save this list to <code>ex_2_4</code>.</p>

<div class="exercise-expected">
<p><strong>Expected result:</strong></p>
<pre><code>#&gt; $status
#&gt; [1] 200
#&gt;
#&gt; $content_type
#&gt; [1] &quot;application/json&quot;
#&gt;
#&gt; $server
#&gt; [1] &quot;cloudflare&quot;</code></pre>