[notes] - bell curves

scripts/generate-bell-curve.js

@@ -0,0 +1,57 @@
+// Generates a bell curve SVG and writes it to _includes/bell-curve.svg
+// Usage: node scripts/generate-bell-curve.js
+
+const fs = require("fs");
+const path = require("path");
+
+const width = 600;
+const height = 300;
+const padding = { top: 20, right: 20, bottom: 40, left: 20 };
+
+const plotW = width - padding.left - padding.right;
+const plotH = height - padding.top - padding.bottom;
+
+// Standard normal PDF
+function gaussian(x) {
+  return Math.exp(-0.5 * x * x) / Math.sqrt(2 * Math.PI);
+}
+
+// Generate points from -4 to 4
+const steps = 200;
+const xMin = -4, xMax = 4;
+const points = [];
+for (let i = 0; i <= steps; i++) {
+  const x = xMin + (xMax - xMin) * (i / steps);
+  points.push({ x, y: gaussian(x) });
+}
+
+const yMax = gaussian(0); // peak value
+
+function sx(x) {
+  return padding.left + ((x - xMin) / (xMax - xMin)) * plotW;
+}
+
+function sy(y) {
+  return padding.top + plotH - (y / yMax) * plotH;
+}
+
+// Build the curve path
+const linePath = points.map((p, i) => {
+  const cmd = i === 0 ? "M" : "L";
+  return `${cmd}${sx(p.x).toFixed(2)},${sy(p.y).toFixed(2)}`;
+}).join(" ");
+
+// Build the filled area path (closed along the baseline)
+const areaPath = linePath
+  + ` L${sx(xMax).toFixed(2)},${sy(0).toFixed(2)}`
+  + ` L${sx(xMin).toFixed(2)},${sy(0).toFixed(2)} Z`;
+
+const svg = `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 ${width} ${height}" role="img" aria-label="Standard normal distribution (bell curve)">
+  <path d="${areaPath}" fill="#d0d0d0" opacity="0.5"/>
+  <path d="${linePath}" fill="none" stroke="currentColor" stroke-width="2"/>
+  <line x1="${sx(xMin)}" y1="${sy(0)}" x2="${sx(xMax)}" y2="${sy(0)}" stroke="currentColor" stroke-width="1"/>
+</svg>`;
+
+const outPath = path.join(__dirname, "..", "_includes", "bell-curve.svg");
+fs.writeFileSync(outPath, svg);
+console.log(`Wrote ${outPath}`);