observablehq · Fil · May 30, 2022 · May 30, 2022
diff --git a/README.md b/README.md
@@ -2250,8 +2250,6 @@ The following aggregation methods are supported:
 * a function to be passed the array of values for each bin and the extent of the bin
 * an object with a *reduce* method
 
-When the hexbin transform has an *r* output channel, bins are returned in order of descending radius.
-
 See also the [hexgrid](#hexgrid) mark.
 
 ### Custom initializers

diff --git a/src/transforms/hexbin.js b/src/transforms/hexbin.js
@@ -27,7 +27,8 @@ export function hexbin(outputs = {fill: "count"}, inputs = {}) {
 
   // Populate default values for the r and symbol options, as appropriate.
   if (options.symbol === undefined) options.symbol = "hexagon";
-  if (options.r === undefined && !hasOutput(outputs, "r")) options.r = binWidth / 2;
+  if (hasOutput(outputs, "r")) options.r = []; // hint that r channel will exist (e.g., for dot to sort)
+  else if (options.r === undefined) options.r = binWidth / 2;
 
   return initializer(options, (data, facets, {x: X, y: Y, z: Z, fill: F, stroke: S, symbol: Q}, scales) => {
     if (X === undefined) throw new Error("missing channel: x");

diff --git a/test/output/hexbin.svg b/test/output/hexbin.svg
diff --git a/test/output/hexbinR.html b/test/output/hexbinR.html
diff --git a/test/output/hexbinSymbol.html b/test/output/hexbinSymbol.html
diff --git a/test/output/hexbinZ.html b/test/output/hexbinZ.html
diff --git a/test/output/hexbinZNull.svg b/test/output/hexbinZNull.svg