sort bins

src/transforms/bin.js

@@ -2,7 +2,7 @@ import {bin as binner, extent, thresholdFreedmanDiaconis, thresholdScott, thresh
 import {valueof, range, identity, maybeLazyChannel, maybeTuple, maybeColor, maybeValue, mid, labelof, isTemporal} from "../mark.js";
 import {offset} from "../style.js";
 import {basic} from "./basic.js";
-import {maybeGroup, maybeOutputs, maybeReduce, maybeSubgroup, reduceIdentity} from "./group.js";
+import {extractOutputs, maybeGroup, maybeOutputs, maybeReduce, maybeSort, maybeSubgroup, reduceIdentity} from "./group.js";
 
 // Group on {z, fill, stroke}, then optionally on y, then bin x.
 export function binX(outputs = {y: "count"}, {inset, insetLeft, insetRight, ...options} = {}) {
@@ -33,7 +33,7 @@ function binn(
   by, // optionally bin on y (exclusive with gy)
   gx, // optionally group on x (exclusive with bx and gy)
   gy, // optionally group on y (exclusive with by and gx)
-  {data: reduceData = reduceIdentity, ...outputs} = {}, // output channel definitions
+  {data: reduceData = reduceIdentity, reverse, ...outputs} = {}, // output channel definitions
   inputs = {} // input channels and options
 ) {
   bx = maybeBin(bx);
@@ -116,12 +116,13 @@ function binn(
         }
         groupFacets.push(groupFacet);
       }
+      maybeSort(groupFacets, outputs, reverse);
       return {data: groupData, facets: groupFacets};
     }),
     ...BX1 ? {x1: BX1, x2: BX2, x: mid(BX1, BX2)} : {x},
     ...BY1 ? {y1: BY1, y2: BY2, y: mid(BY1, BY2)} : {y},
     ...GK && {[gk]: GK},
-    ...Object.fromEntries(outputs.map(({name, output}) => [name, output]))
+    ...extractOutputs(outputs)
   };
 }
 

src/transforms/group.js

@@ -1,5 +1,5 @@
 import {group as grouper, sort, sum, deviation, min, max, mean, median, mode, variance, InternSet} from "d3";
-import {firstof} from "../defined.js";
+import {ascendingDefined, firstof} from "../defined.js";
 import {valueof, maybeColor, maybeInput, maybeTuple, maybeLazyChannel, lazyChannel, first, identity, take, labelof, range} from "../mark.js";
 import {basic} from "./basic.js";
 
@@ -34,7 +34,7 @@ export function group(outputs, options = {}) {
 function groupn(
   x, // optionally group on x
   y, // optionally group on y
-  {data: reduceData = reduceIdentity, ...outputs} = {}, // output channel definitions
+  {data: reduceData = reduceIdentity, reverse, ...outputs} = {}, // output channel definitions
   inputs = {} // input channels and options
 ) {
   reduceData = maybeReduce(reduceData, identity);
@@ -93,11 +93,12 @@ function groupn(
         }
         groupFacets.push(groupFacet);
       }
+      maybeSort(groupFacets, outputs, reverse);
       return {data: groupData, facets: groupFacets};
     }),
     ...GX && {x: GX},
     ...GY && {y: GY},
-    ...Object.fromEntries(outputs.map(({name, output}) => [name, output]))
+    ...extractOutputs(outputs)
   };
 }
 
@@ -163,6 +164,24 @@ export function maybeSubgroup(outputs, Z, F, S) {
   );
 }
 
+export function maybeSort(facets, outputs, reverse) {
+  const sort = outputs.find(o => o.name === "sort");
+  if (sort) {
+    const S = sort.output.transform();
+    const compare = (i, j) => ascendingDefined(S[i], S[j]);
+    facets.forEach(f => f.sort(compare));
+  }
+  if (reverse) {
+    facets.forEach(f => f.reverse());
+  }
+}
+
+export function extractOutputs(outputs) {
+  return Object.fromEntries(outputs
+    .filter(({name}) => name !== "sort")
+    .map(({name, output}) => [name, output]));
+}
+
 function reduceFunction(f) {
   return {
     reduce(I, X) {