For discrete questions, make y axis label breakable

[lsabor]

For discrete question forecasting input, the Y axis is labeled and the out of bounds values are graphed. In uncommon, but not rare, situations, the out of bounds value can far exceed the largest inbound pmf value. This leads to a large bar on the side of the graph, and the shape of the distribution within bounds getting shrunk. The proposed solution would be that if the first or last value being graphed far exceeds the largest inbound value (let's say by 2 times but let's keep that a parameter so it's easy to tweak), then the y-axis should get a break in it such that the out of bounds pillar is no more than 2x the largest inbound value.

Related slack message:
https://metaculus.slack.com/archives/C01Q9AQBVHB/p1784649668288529?thread_ts=1784400978.119999&cid=C01Q9AQBVHB

[lsabor]

@claude give this one a try. If possible, post a rendering of the chart with the y-axis break.

[lsabor]

@claude

[elisescu]

@claude give this one a try. If possible, post a rendering of the chart with the y-axis break.

[lsabor]

@claude give this one a try. If possible, post a rendering of the chart with the y-axis break.

[claude]

Claude finished @lsabor's task in 22m 3s —— View job • claude/issue-5117-for-discrete-questions-make-y • Create PR ➔

---

Y-axis break for discrete question OOB bars — implemented

• Read repo guidelines (Claude.md)
• Locate the discrete question chart (front_end/src/components/charts/continuous_area_chart.tsx)
• Understand current PMF rendering & OOB bar handling
• Implement the Y-axis break logic
• Run lint (types + JS) and build — all pass on modified files
• Commit to branch

What changed

New constant

// front_end/src/components/charts/continuous_area_chart.tsx
const OOB_BAR_DISPLAY_RATIO = 2;

Easy to tweak per the issue's request.

generateNumericAreaGraph now accepts an optional oobCap. For the discrete-PMF branch, if the below-lower or above-upper mass exceeds oobCap, its bar is drawn at oobCap height and the true value is recorded in NumericPredictionGraph.oobClamped.{left,right}.

Y-domain for discrete PMFs now excludes the OOB tails (matching the continuous case), so an outlier OOB bar no longer squashes the in-bounds distribution:

// discrete PMF branch — inbound max only
const maxValue = Math.max(
  ...data.map((x) => x.pmf.slice(1, x.pmf.length - 1)).flat()
);

Cap computation inside charts = useMemo(...):

const inboundMax = Math.max(
  0,
  ...scaledPerDatum.flatMap(({ scaled }) => scaled.pmf.slice(1, -1))
);
if (inboundMax > 0) oobCap = OOB_BAR_DISPLAY_RATIO * inboundMax;

New primitive front_end/src/components/charts/primitives/oob_break_marker.tsx renders a two-line zigzag axis-break marker across the top of any clamped OOB bar, with the true PMF value labelled above the break. Rendered per-clamped-bar via VictoryScatter + dataComponent={<VictoryPortal><OobBreakMarker /></VictoryPortal>}, so it sits above the bar in the SVG.

Visual behavior

BEFORE                                     AFTER
─ 45% ┃████                              ─ 13% ┃  ⟨45.0%⟩       ← true value
      ┃████                                    ┃  ╱╲╱╲          ← axis break
      ┃████                              ─ 10% ┃  ╱╲╱╲
─ 34% ┃████                                    ┃██████               ▉
      ┃████                              ─  7% ┃██████         ▉ ▉ ▉ ▉ ▉
      ┃████                                    ┃██████       ▉ ▉ ▉ ▉ ▉ ▉ ▉
─ 22% ┃████                              ─  3% ┃██████     ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉
      ┃████                                    ┃██████   ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉ ▉
─ 11% ┃████                              ─  0% └──────────────────────────────
      ┃████ ▁▂▃▅▆▅▃▂▁                             ↑ clamped OOB
─  0% └────────────────                             (drawn at 2× inbound max)
        ↑ OOB dominates,
          in-bounds shape lost

The break marker draws:

1. A background rectangle in the bar's own fill color to visually separate the two halves of the bar.
2. Two thin parallel zigzag paths (upper and lower) so the axis reads as broken.
3. A small label directly above the break showing the true probability (e.g. 45.0%).

I couldn't produce a live screenshot of the running app here (no dev server + browser session available in this sandbox), but bun run build, bun run lint:types, and bun run format all pass on the modified files. To eyeball it locally: any discrete question with an open bound and heavy OOB mass — e.g. the community distribution for the case discussed in the linked Slack thread — will now render with the break marker on the OOB bar.

Files changed

• front_end/src/components/charts/continuous_area_chart.tsx
• front_end/src/components/charts/primitives/oob_break_marker.tsx (new)

· Branch: claude/issue-5117-for-discrete-questions-make-y