fix: return +Infinity at x = 0 for k < 1 in stats/base/dists/weibull/pdf and logpdf

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/lib/factory.js

@@ -78,6 +78,10 @@ function factory( k, lambda ) {
 			return NINF;
 		}
 		if ( x === 0.0 ) {
+			// The density at `0` is infinite for `k < 1`, `1/lambda` for `k = 1`, and `0` for `k > 1`:
+			if ( k < 1.0 ) {
+				return PINF;
+			}
 			return ( k === 1.0 ) ? ln( k / lambda ) : NINF;
 		}
 		xol = x / lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/lib/main.js

@@ -82,6 +82,10 @@ function logpdf( x, k, lambda ) {
 		return NINF;
 	}
 	if ( x === 0.0 ) {
+		// The density at `0` is infinite for `k < 1`, `1/lambda` for `k = 1`, and `0` for `k > 1`:
+		if ( k < 1.0 ) {
+			return PINF;
+		}
 		return ( k === 1.0 ) ? ln( k/lambda ): NINF;
 	}
 	xol = x / lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/src/main.c

@@ -52,6 +52,10 @@ double stdlib_base_dists_weibull_logpdf( const double x, const double k, const d
 		return STDLIB_CONSTANT_FLOAT64_NINF;
 	}
 	if ( x == 0.0 ) {
+		// The density at `0` is infinite for `k < 1`, `1/lambda` for `k = 1`, and `0` for `k > 1`:
+		if ( k < 1.0 ) {
+			return STDLIB_CONSTANT_FLOAT64_PINF;
+		}
 		return ( k == 1.0 ) ? stdlib_base_ln( k/lambda ) : STDLIB_CONSTANT_FLOAT64_NINF;
 	}
 	xol = x / lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/test/test.factory.js

@@ -189,7 +189,7 @@ tape( 'if provided a positive `lambda` and `k` equal to one, the created functio
 	t.end();
 });
 
-tape( 'if provided a positive `lambda` and `k` not equal to one, the  created function returns `-infinity` for `x=0`', function test( t ) {
+tape( 'if provided a positive `lambda` and `k` greater than one, the created function returns `-infinity` for `x=0`', function test( t ) {
 	var logpdf;
 	var y;
 
@@ -199,6 +199,16 @@ tape( 'if provided a positive `lambda` and `k` not equal to one, the  created fu
 	t.end();
 });
 
+tape( 'if provided a positive `lambda` and `k` less than one, the created function returns `+infinity` for `x=0`', function test( t ) {
+	var logpdf;
+	var y;
+
+	logpdf = factory( 0.5, 1.0 );
+	y = logpdf( 0.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the created function evaluates the logpdf for `x` given large `lambda` and `k`', function test( t ) {
 	var expected;
 	var logpdf;

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/test/test.logpdf.js

@@ -133,12 +133,18 @@ tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` equal to one, the
 	t.end();
 });
 
-tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` not equal to one, the function returns `-Infinity`', function test( t ) {
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` greater than one, the function returns `-Infinity`', function test( t ) {
 	var y = logpdf( 0.0, 2.0, 1.0 );
 	t.strictEqual( y, NINF, 'returns expected value' );
 	t.end();
 });
 
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` less than one, the function returns `+Infinity`', function test( t ) {
+	var y = logpdf( 0.0, 0.5, 1.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function evaluates the logpdf for `x` given large `lambda` and `k`', function test( t ) {
 	var expected;
 	var lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/logpdf/test/test.native.js

@@ -142,12 +142,18 @@ tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` equal to one, the
 	t.end();
 });
 
-tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` not equal to one, the function returns `-Infinity`', opts, function test( t ) {
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` greater than one, the function returns `-Infinity`', opts, function test( t ) {
 	var y = logpdf( 0.0, 2.0, 1.0 );
 	t.strictEqual( y, NINF, 'returns expected value' );
 	t.end();
 });
 
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` less than one, the function returns `+Infinity`', opts, function test( t ) {
+	var y = logpdf( 0.0, 0.5, 1.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function evaluates the logpdf for `x` given large `lambda` and `k`', opts, function test( t ) {
 	var expected;
 	var lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/pdf/lib/factory.js

@@ -77,6 +77,10 @@ function factory( k, lambda ) {
 			return 0.0;
 		}
 		if ( x === 0.0 ) {
+			// The density at `0` is infinite for `k < 1`, `1/lambda` for `k = 1`, and `0` for `k > 1`:
+			if ( k < 1.0 ) {
+				return PINF;
+			}
 			return ( k === 1.0 ) ? k / lambda : 0.0;
 		}
 		xol = x / lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/pdf/lib/main.js

@@ -83,6 +83,10 @@ function pdf( x, k, lambda ) {
 		return 0.0;
 	}
 	if ( x === 0.0 ) {
+		// The density at `0` is infinite for `k < 1`, `1/lambda` for `k = 1`, and `0` for `k > 1`:
+		if ( k < 1.0 ) {
+			return PINF;
+		}
 		return ( k === 1.0 ) ? k/lambda : 0.0;
 	}
 	xol = x / lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/pdf/test/test.factory.js

@@ -186,7 +186,7 @@ tape( 'if provided a positive `lambda` and `k` equal to one, the created functio
 	t.end();
 });
 
-tape( 'if provided a positive `lambda` and `k` not equal to one, the  created function returns `0` for `x=0`', function test( t ) {
+tape( 'if provided a positive `lambda` and `k` greater than one, the created function returns `0` for `x=0`', function test( t ) {
 	var pdf;
 	var y;
 
@@ -196,6 +196,16 @@ tape( 'if provided a positive `lambda` and `k` not equal to one, the  created fu
 	t.end();
 });
 
+tape( 'if provided a positive `lambda` and `k` less than one, the created function returns `+infinity` for `x=0`', function test( t ) {
+	var pdf;
+	var y;
+
+	pdf = factory( 0.5, 1.0 );
+	y = pdf( 0.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the created function evaluates the pdf for `x` given large `lambda` and `k`', function test( t ) {
 	var expected;
 	var lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/pdf/test/test.native.js

@@ -140,12 +140,18 @@ tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` equal to one, the
 	t.end();
 });
 
-tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` not equal to one, the function returns `0`', opts, function test( t ) {
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` greater than one, the function returns `0`', opts, function test( t ) {
 	var y = pdf( 0.0, 2.0, 1.0 );
 	t.strictEqual( y, 0.0, 'returns expected value' );
 	t.end();
 });
 
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` less than one, the function returns `+Infinity`', opts, function test( t ) {
+	var y = pdf( 0.0, 0.5, 1.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function evaluates the pdf for `x` given large `lambda` and `k`', opts, function test( t ) {
 	var expected;
 	var lambda;

lib/node_modules/@stdlib/stats/base/dists/weibull/pdf/test/test.pdf.js

@@ -131,12 +131,18 @@ tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` equal to one, the
 	t.end();
 });
 
-tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` not equal to one, the function returns `0`', function test( t ) {
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` greater than one, the function returns `0`', function test( t ) {
 	var y = pdf( 0.0, 2.0, 1.0 );
 	t.strictEqual( y, 0.0, 'returns expected value' );
 	t.end();
 });
 
+tape( 'if provided `0.0` for `x`, a positive `lambda` and `k` less than one, the function returns `+Infinity`', function test( t ) {
+	var y = pdf( 0.0, 0.5, 1.0 );
+	t.strictEqual( y, PINF, 'returns expected value' );
+	t.end();
+});
+
 tape( 'the function evaluates the pdf for `x` given large `lambda` and `k`', function test( t ) {
 	var expected;
 	var lambda;