the denseInterval option for k must also reduce k1 and k2 if present

src/transforms/bin.js

@@ -67,9 +67,13 @@ export function bin(outputs = {fill: "count"}, options = {}) {
 }
 
 function maybeDenseInterval(bin, k, options = {}) {
-  return options?.interval == null
-    ? options
-    : bin({[k]: options?.reduce === undefined ? reduceFirst : options.reduce, filter: null}, options);
+  if (options?.interval == null) return options;
+  const {reduce = reduceFirst} = options;
+  const outputs = {filter: null};
+  if (options[k] != null) outputs[k] = reduce;
+  if (options[`${k}1`] != null) outputs[`${k}1`] = reduce;
+  if (options[`${k}2`] != null) outputs[`${k}2`] = reduce;
+  return bin(outputs, options);
 }
 
 export function maybeDenseIntervalX(options = {}) {

test/plots/aapl-interval.ts

@@ -0,0 +1,7 @@
+import * as Plot from "@observablehq/plot";
+import * as d3 from "d3";
+
+export async function aaplInterval() {
+  const aapl = await d3.csv<any>("data/aapl.csv", d3.autoType);
+  return Plot.areaY(aapl.slice(0, 81), {x: "Date", y1: "Low", y2: "High", interval: "day", curve: "step"}).plot();
+}

test/plots/index.ts

@@ -4,6 +4,7 @@ export * from "./aapl-change-volume.js";
 export * from "./aapl-close-untyped.js";
 export * from "./aapl-close.js";
 export * from "./aapl-fancy-axis.js";
+export * from "./aapl-interval.js";
 export * from "./aapl-monthly.js";
 export * from "./aapl-volume-rect.js";
 export * from "./aapl-volume.js";