js functions that i need often and i am NOT making another npm package, fuck that

vercajch.js

// like python's range, yields numbers from start to end (not inclusive)
export const range = function* (start, end, step = 1) {
  let index = start;
  while (index < end) {
    yield index;
    index++;
  }
}

// like python's enumerate, yields [index, item]
export function* enumerate(iterable) {
  let count = 0;
  for (let item of iterable) {
    yield [count++, item];
  }
}

// returns a randomly selected item from a given array
export const choose = list => list[Math.floor(Math.random() * list.length)];

// converts degress to radians
export const rad = x => (x * Math.PI) / 180;

// converts radians to degrees
export const deg = x => (x * 180) / Math.PI;

// aint installing no lodash
// https://stackoverflow.com/a/27078401
export const throttle = (callback, wait) => {
  let go = true;
  return () => {
    if (go) {
      go = false;
      setTimeout(() => {
        go = true;
        callback.call();
      }, wait);
    }
  };
};

// returns the sum of numbers in the given array
export const sum = (vector) => {
    let s = 0;

    for (var i = 0; i < vector.length; i++) {
        s += vector[i];
    }

    return s;
};

// returns the mean of numbers in the given array
export const mean = (vector) => {
    return sum(vector) / vector.length;
};

// returns the variance of numbers in the given array
export const variance = (vectorMean, vector) => {
    let s = 0;

    for (let i = 0; i < vector.length; i++) {
        s += (vector[i] - vectorMean) ** 2;
    }

    return s;
}

/**
 * Standard deviation with N-1 normalisation factor
 * which matches Matlab's `std` with the default `w` parameter
 *
 * @param {Array} vectorMean mean of the provided vector (provided separately for modularity)
 * @param {Array} vector the vector itself
 */
export const stddev = (vectorMean, vector) => {
    return Math.sqrt(variance(vectorMean, vector) / (vector.length - 1));
}