previousInterpolation function

UnaryFunction<double> previousInterpolation({ required Vector<double> xs, required Vector<double> ys, double left = double.nan, })

A function providing the previous value of a discrete monotonically increasing set of sample points xs and ys. Returns left if there is no previous sample point.

Implementation

UnaryFunction<double> previousInterpolation({
  required Vector<double> xs,
  required Vector<double> ys,
  double left = double.nan,
}) {
  checkPoints(
    DataType.float,
    xs: xs,
    ys: ys,
    min: 1,
    ordered: true,
    unique: true,
  );
  return (double x) {
    if (x < xs.getUnchecked(0)) {
      return left;
    } else if (xs.getUnchecked(xs.count - 1) < x) {
      return ys.getUnchecked(ys.count - 1);
    } else {
      return ys.getUnchecked(
        DataType.float.comparator.binarySearchRight(xs, x).clamp(1, xs.count) -
            1,
      );
    }
  };
}