fix: mode signature return types

[rich-martinez]

Reason(s) For Change

• Using mode with and array of numbers seems to always return array of numbers regardless of how many modes are found
• The mode function seems to only ever return an array:

  mathjs/src/function/statistics/mode.js

  Lines 41 to 78 in cee9deb

  	/**
  	* Calculates the mode in an 1-dimensional array
  	* @param {Array} values
  	* @return {Array} mode
  	* @private
  	*/
  	function _mode (values) {
  	values = flatten(values.valueOf())
  	const num = values.length
  	if (num === 0) {
  	throw new Error('Cannot calculate mode of an empty array')
  	}
  	const count = {}
  	let mode = []
  	let max = 0
  	for (let i = 0; i < values.length; i++) {
  	const value = values[i]
  	if (isNumeric(value) && isNaN(value)) {
  	throw new Error('Cannot calculate mode of an array containing NaN values')
  	}
  	if (!(value in count)) {
  	count[value] = 0
  	}
  	count[value]++
  	if (count[value] === max) {
  	mode.push(value)
  	} else if (count[value] > max) {
  	max = count[value]
  	mode = [value]
  	}
  	}
  	return mode
  	}

Changes

• Update the mode signatures return types to be an array of current types
• Add mode type tests

Notes

It is unclear if this type needs to change as well, because it seems like it should return an array on done:

mathjs/types/index.d.ts

Line 6125 in cee9deb

mode(this: MathJsChain<MathType[]>): MathJsChain<MathType[]>

[josdejong]

Thanks! Your fixes are indeed correct.

It is unclear if this type needs to change as well, because it seems like it should return an array on done:

mode(this: MathJsChain<MathType[]>): MathJsChain<MathType[]>

I think this type is wrong: in chained function, you can only pass a single Matrix. At first glance I would expect the type to be this:

mode(this: MathJsChain<MathCollection>): MathJsChain<MathCollection>

And the same for the surrounding functions max, mean, median, min, prod. Except for prod, they just have a redundant type definition, the MathCollection variant is there for all but prod.

[rich-martinez]

@josdejong I added mode type tests: https://github.com/josdejong/mathjs/pull/3153/files#diff-66424e9e2afdbff8a82b370e67fe043e56f02224e48d346862a91c50b4b6978bR2545-R2575

Please let me know if I am missing something.

[josdejong]

Thanks Rich, looks good 👌

[josdejong]

Published in v12.4.0, thanks again.