Provide more concise histogram shorthand

[chrispahm]

When working with one-dimensional data, I wish there was a very simple and easy to memorize way to generate a histogram.
Something likes R's / matplotlib's hist(data).

I know there's a Plot shorthand Plot.rectY(data, Plot.binX()).plot(), but it requires much more typing and is less ergenomic. Could something like Plot.hist(data).plot() be an alternative?

In an Observable notebook, what I usually end up doing is that I search and insert the "Histogram chart" snippet instead. The snippet requires an array of objects though, so the one-dimensional data needs to be transformed first. It would be nice to have a simpler solution for these scenarios!

[Fil]

This is what Plot.auto is for.

Plot.auto(numbers, {x: numbers}).plot()

(It would be nice if auto would know how to treat an array of numbers, allowing us to say ``Plot.auto(numbers).plot()`, but it's not yet the case.)

For a slightly different example with an accessor:
Plot.auto({ length: 10000 }, { x: Math.random }).plot()

[chrispahm]

If Plot.auto(numbers).plot() would work, that would be great!

Is there a more general reason why a simple check like Array.isArray(firstArg) && firstArg.every(d => typeof x === "number")
(or something similar) wouldn't work to auto distinguish if the input is an array of numbers?

[chrispahm]

Guess this is the relevant section

plot/src/marks/auto.js

Lines 15 to 17 in 48b71d7

	export function autoSpec(data, options) {
	options = normalizeOptions(options);

so a simple check like this would probably be enough?

export function autoSpec(data, options) {
  // Determine if data is an array of numbers.
  if (Array.isArray(data) && !options && data.every(d => typeof x === "number")) {
    options = { x: data }
  }
  options = normalizeOptions(options);

[Fil]

Yes I think we'd want something like that. We should also support typed arrays (those don't need a value check), as well as arrays of Date objects. Also usually we only detect the type of contents from the first non-nullish value, see for example

plot/src/options.js

Line 412 in 48b71d7

export function isTemporal(values) {

[mbostock]

I feel like we could add

Plot.histX(data, options?)

as shorthand for

Plot.rectY(data, Plot.binX(undefined, options?))

I’m not sure it’s that useful, though… I imagine you’ll hit a wall pretty quickly which is primarily why we don’t offer this.

[chrispahm]

Thanks for the clarification! I think it would be great if Plot.auto would support an array of numbers like @Fil described. I updated the snippet above to include his suggestions, so probably this little change would be sufficient?

// ...
import {isColor, isNumeric, isObject, isOptions, isOrdinal, isTemporal, labelof, valueof} from "../options.js";
// ...

export function autoSpec(data, options) {
  // Determine if data is an array of numbers or dates.
  if (Array.isArray(data) && !options && (ArrayBuffer.isView(data) || isNumeric(data) || isTemporal(data)) ) {
    options = { x: data };
  }
  options = normalizeOptions(options);

If desired I can create a PR as well.