maia-util/es6/median.js

Utility math and music functions supporting various applications by Music Artificial Intelligence Algorithms, Inc.

export default function median(arr){
  // Tom Collins 28/8/2020.
  // In
  // arr Array mandatory
  // Out Number
  // This function returns the median of an input numeric array. No assumption
  // of sortedness. Tests input is all of type number, returning undefined if
  // this tests fails.

  if (arr.length === 0){
    return
  }
  const testAllNum = arr.every(function(x){ return typeof x === "number" })
  if (!testAllNum){
    console.log(
      "arr contains the wrong data types or is a mix of data types. " +
      "Returning undefined."
    )
    return
  }
  let sortedArr = arr.sort(function(x, y){
    return x - y
  })
  let n = sortedArr.length
  if (n % 2 == 0){
    return (sortedArr[n/2 - 1] + sortedArr[n/2])/2
  }
  else {
    return sortedArr[(n - 1)/2]
  }
}