code: function forecastErrors(actuals, estimates) {
                if (actuals.length !== estimates.length) throw new Error(`Actuals length (${actuals.length}) must equal Estimates length (${estimates.length})`);
                return actuals.map((act, i) => act - estimates[ i ]);
              }
docs: The errors (residuals) from acutals and estimates
  @memberOf util
  @example
  const actuals = [ 45, 38, 43, 39 ];
  const estimates = [ 41, 43, 41, 42 ];
  const errors = ms.util.forecastErrors(actuals, estimates); // => [ 4, -5, 2, -3 ]
  @param {Number[]} actuals - numerical samples
  @param {Number[]} estimates - estimates values
  @returns {Number[]} errors (residuals)