@jrc03c/js-math-tools/src/transpose.mjs

some math tools for JS

import { assert } from "./assert.mjs"
import { isArray } from "./is-array.mjs"
import { isDataFrame } from "./is-dataframe.mjs"
import { isSeries } from "./is-series.mjs"
import { ndarray } from "./ndarray.mjs"
import { reverse } from "./reverse.mjs"
import { shape } from "./shape.mjs"

function transpose(arr) {
  if (isDataFrame(arr) || isSeries(arr)) {
    return arr.transpose()
  }

  assert(
    isArray(arr),
    "The `transpose` function only works on arrays, Series, and DataFrames!",
  )

  const theShape = shape(arr)

  assert(
    theShape.length <= 2,
    "I'm not smart enough to know how to transpose arrays that have more than 2 dimensions. Sorry for the inconvenience! Please only pass 1- or 2-dimensional arrays into the `transpose` function!",
  )

  if (theShape.length === 1) {
    return reverse(arr)
  } else if (theShape.length === 2) {
    const out = ndarray(reverse(theShape))

    for (let row = 0; row < theShape[0]; row++) {
      for (let col = 0; col < theShape[1]; col++) {
        out[col][row] = arr[row][col]
      }
    }

    return out
  }
}

export { transpose }