code: function percentile(arr, p) {
      if (arr.length === 0) return 0;
      if (typeof p !== 'number') throw new TypeError('p must be a number');
      if (p <= 0) return arr[0];
      if (p >= 1) return arr[arr.length - 1];
  
      var index = arr.length * p,
          lower = Math.floor(index),
          upper = lower + 1,
          weight = index % 1;
  
      if (upper >= arr.length) return arr[lower];
      return arr[lower] * (1 - weight) + arr[upper] * weight;
  }
docs: From https://gist.github.com/IceCreamYou/6ffa1b18c4c8f6aeaad2 Returns the value at a given percentile in a sorted numeric array. "Linear interpolation between closest ranks" method