consistent groups

src/transforms/bin.js

@@ -2,6 +2,7 @@ import {bin as binner, cross, group, sum} from "d3";
 import {firstof} from "../defined.js";
 import {valueof, first, second, range, identity, lazyChannel, maybeLazyChannel, maybeTransform, maybeColor, maybeValue, mid, take, labelof} from "../mark.js";
 import {offset} from "../style.js";
+import {groups} from "./group.js";
 
 // Group on y, z, fill, or stroke, if any, then bin on x.
 export function binX({x, y, out = y == null ? "y" : "fill", inset, insetLeft, insetRight, ...options} = {}) {
@@ -162,7 +163,7 @@ function bin2(x, y, {weight, domain, thresholds, normalize, z, fill, stroke, ...
         let i = 0;
         for (const facet of facets) {
           const binFacet = [];
-          for (const I of G ? group(facet, i => G[i]).values() : [facet]) {
+          for (const [, I] of groups(facet, G)) {
             if (normalize === "z") n = W ? sum(I, i => W[i]) : I.length;
             const set = new Set(I);
             for (const b of B) {

src/transforms/group.js

@@ -85,10 +85,10 @@ function group2(xv, yv, {z, fill, stroke, weight, domain, normalize, ...options}
         for (const facet of facets) {
           const groupFacet = [];
           if (normalize === "facet") n = W ? sum(facet, i => W[i]) : facet.length;
-          for (const I of G ? grouper(facet, i => G[i]).values() : [facet]) {
+          for (const [, I] of groups(facet, G, defined1)) {
             if (normalize === "z") n = W ? sum(I, i => W[i]) : I.length;
-            for (const [y, fy] of Y ? sort(grouper(I, i => Y[i]), first).filter(ydefined) : [[, I]]) {
-              for (const [x, f] of X ? sort(grouper(fy, i => X[i]), first).filter(xdefined) : [[, fy]]) {
+            for (const [y, fy] of groups(I, Y, ydefined)) {
+              for (const [x, f] of groups(fy, X, xdefined)) {
                 const l = W ? sum(f, i => W[i]) : f.length;
                 groupFacet.push(i++);
                 groupData.push(take(data, f));
@@ -119,10 +119,6 @@ function maybeDomain(domain) {
   return ([key]) => domain.has(key);
 }
 
-function defined1([key]) {
-  return defined(key);
-}
-
 function maybeNormalize(normalize) {
   if (!normalize) return;
   if (normalize === true) return 100;
@@ -132,3 +128,11 @@ function maybeNormalize(normalize) {
   }
   throw new Error("invalid normalize");
 }
+
+function defined1([key]) {
+  return defined(key);
+}
+
+export function groups(I, X, defined = defined1) {
+  return X ? sort(grouper(I, i => X[i]), first).filter(defined) : [[, I]];
+}

test/plots/penguin-species-group.js

@@ -4,11 +4,9 @@ import * as d3 from "d3";
 export default async function() {
   const penguins = await d3.csv("data/penguins.csv", d3.autoType);
   return Plot.plot({
-    x: {
-      grid: true
-    },
     marks: [
       Plot.barX(penguins, Plot.stackX(Plot.groupZX({fill: "species", normalize: true}))),
+      Plot.text(penguins, Plot.stackXMid(Plot.groupZX({z: "species", normalize: true, text: ([d]) => d.species}))),
       Plot.ruleX([0, 100])
     ]
   });