add Plot.shuffle (#564)

* add Plot.shuffle

* add seed option for deterministic shuffle

Author: mbostock

README.md

@@ -1047,6 +1047,14 @@ Plot.sort("body_mass_g", options) // show data in ascending body mass order
 
 Sorts the data by the specified *order*, which can be an accessor function, a comparator function, or a channel value definition such as a field name.
 
+### Plot.shuffle(*options*)
+
+```js
+Plot.shuffle(options) // show data in random order
+```
+
+Shuffles the data randomly. If a *seed* option is specified, a linear congruential generator with the given seed is used to generate random numbers deterministically; otherwise, Math.random is used.
+
 ### Plot.reverse(*options*)
 
 ```js

src/index.js

@@ -13,7 +13,7 @@ export {Text, text, textX, textY} from "./marks/text.js";
 export {TickX, TickY, tickX, tickY} from "./marks/tick.js";
 export {filter} from "./transforms/filter.js";
 export {reverse} from "./transforms/reverse.js";
-export {sort} from "./transforms/sort.js";
+export {sort, shuffle} from "./transforms/sort.js";
 export {bin, binX, binY} from "./transforms/bin.js";
 export {group, groupX, groupY, groupZ} from "./transforms/group.js";
 export {normalize, normalizeX, normalizeY} from "./transforms/normalize.js";

src/transforms/sort.js

@@ -1,7 +1,12 @@
+import {randomLcg} from "d3";
 import {ascendingDefined} from "../defined.js";
 import {valueof} from "../mark.js";
 import {basic} from "./basic.js";
 
+export function shuffle({seed, ...options} = {}) {
+  return basic(options, sortValue(seed == null ? Math.random : randomLcg(seed)));
+}
+
 export function sort(value, options) {
   return basic(options, sortTransform(value));
 }