heatmaps: part 6

website/src/heatmap/grid.js

@@ -0,0 +1,136 @@
+/** @import { HeatmapGrid, HeatmapGridFactory, HeatmapRange } from "./types.js" */
+
+/**
+ * @param {number} value
+ * @param {number} min
+ * @param {number} max
+ */
+function clamp(value, min, max) {
+  return Math.min(max, Math.max(min, value));
+}
+
+/**
+ * Generic date/y binning with average merge semantics.
+ *
+ * @param {Object} args
+ * @param {number} args.yStart
+ * @param {number} args.yEnd
+ * @param {number} [args.minCellSize]
+ * @param {number} [args.maxCols]
+ * @param {number} [args.nativeRows]
+ * @returns {HeatmapGridFactory}
+ */
+export function createAverageGrid({
+  yStart,
+  yEnd,
+  minCellSize = 1,
+  maxCols = Number.POSITIVE_INFINITY,
+  nativeRows = Number.POSITIVE_INFINITY,
+}) {
+  return {
+    create({ dates, width, height }) {
+      const cols = Math.max(
+        1,
+        Math.min(
+          dates.length || 1,
+          maxCols,
+          Math.floor(width / minCellSize) || 1,
+        ),
+      );
+      const rows = Math.max(
+        1,
+        Math.min(nativeRows, Math.floor(height / minCellSize) || 1),
+      );
+      const sums = new Float64Array(cols * rows);
+      const counts = new Uint32Array(cols * rows);
+      const ySpan = yEnd - yStart;
+
+      /** @param {number} dateIndex */
+      function toCol(dateIndex) {
+        if (dateIndex < 0 || dateIndex >= dates.length) return undefined;
+        return clamp(Math.floor((dateIndex * cols) / dates.length), 0, cols - 1);
+      }
+
+      /** @param {number} y */
+      function toRow(y) {
+        if (!Number.isFinite(y) || !Number.isFinite(ySpan) || ySpan <= 0) {
+          return undefined;
+        }
+        const t = (y - yStart) / ySpan;
+        if (t < 0 || t > 1) return undefined;
+        return rows - 1 - clamp(Math.floor(t * rows), 0, rows - 1);
+      }
+
+      /**
+       * @param {number} dateIndex
+       * @param {number} y
+       * @param {number} value
+       */
+      function addValue(dateIndex, y, value) {
+        if (!Number.isFinite(value)) return undefined;
+        const col = toCol(dateIndex);
+        const row = toRow(y);
+        if (col === undefined || row === undefined) return undefined;
+        const index = row * cols + col;
+        sums[index] += value;
+        counts[index] += 1;
+        return col;
+      }
+
+      /** @type {HeatmapGrid} */
+      const grid = {
+        dates,
+        cols,
+        rows,
+        add(dateIndex, points) {
+          let dirty;
+          if (points.kind === "implicit") {
+            for (let i = 0; i < points.values.length; i++) {
+              const col = addValue(
+                dateIndex,
+                points.yStart + i * points.yStep,
+                points.values[i],
+              );
+              dirty = col ?? dirty;
+            }
+          } else {
+            const length = Math.min(points.y.length, points.values.length);
+            for (let i = 0; i < length; i++) {
+              const col = addValue(dateIndex, points.y[i], points.values[i]);
+              dirty = col ?? dirty;
+            }
+          }
+          return dirty;
+        },
+        getValue(col, row) {
+          if (col < 0 || col >= cols || row < 0 || row >= rows) {
+            return Number.NaN;
+          }
+          const index = row * cols + col;
+          return counts[index] ? sums[index] / counts[index] : Number.NaN;
+        },
+        getDateIndexRange(col) {
+          if (col < 0 || col >= cols || dates.length === 0) {
+            return emptyRange();
+          }
+          const start = Math.floor((col * dates.length) / cols);
+          const end = Math.floor(((col + 1) * dates.length - 1) / cols);
+          return { start, end: clamp(end, start, dates.length - 1) };
+        },
+        getYRange(row) {
+          if (row < 0 || row >= rows || ySpan <= 0) return emptyRange();
+          const start = yStart + ((rows - row - 1) / rows) * ySpan;
+          const end = yStart + ((rows - row) / rows) * ySpan;
+          return { start, end };
+        },
+      };
+
+      return grid;
+    },
+  };
+}
+
+/** @returns {HeatmapRange} */
+function emptyRange() {
+  return { start: Number.NaN, end: Number.NaN };
+}