module.exports = {
  roundTo2(num) {
    return Math.round((num + Number.EPSILON) * 100) / 100;
  },
  stdDev(array) {
    const n = array.length;
    const mean = array.reduce((a, b) => a + b) / n;
    return Math.sqrt(
      array.map((x) => Math.pow(x - mean, 2)).reduce((a, b) => a + b) / n
    );
  },
  mean(array) {
    try {
      return (
        array.reduce((previous, current) => (current += previous)) /
        array.length
      );
    } catch (e) {
      return 0;
    }
  },
  kogasa(cov) {
    return (
      100 * (1 - Math.tanh(cov + Math.pow(cov, 3) / 3 + Math.pow(cov, 5) / 5))
    );
  },
};