cellxgene/client/src/util/quantile.js

/*
quantiles - calculate quantiles for the typed array.

Currently interpolates to 'lower' value.

Arguments:

	* quantArr - array of quantiles to compute, where values:  0 <= value <= 1.0
	* tarr - a typed array
	* sorted - option bool.  If false (default), will assume array is not sorted.
	 	If true, will assume it is sorted.

*/

import { sortArray } from "./typedCrossfilter/sort";

export default function quantile(quantArr, tarr, sorted = false) {
	/*
	start with the naive (sort) implementation.  Later, use a faster partition
	*/
	const arr = sorted ? tarr : sortArray(new tarr.constructor(tarr)); // copy
	const len = arr.length;
	return quantArr.map(q => {
		if (q === 1) {
			return arr[len - 1];
		}
		return arr[Math.floor(q * len)];
	});
}