/// <summary>A Vector extension method that segments.</summary>
/// <exception cref="InvalidOperationException">Thrown when the requested operation is invalid.</exception>
/// <param name="x">The x to act on.</param>
/// <param name="segments">The segments.</param>
/// <returns>A Range[].</returns>
public static Range[] Segment(this Vector x, int segments)
{
if (segments < 2)
{
throw new InvalidOperationException("Invalid Segment Length, must > 1");
}
// list max and min
var max = x.Max();
var min = x.Min();
// range size
var range = (max - min) / segments;
// create range array
var ranges = new Range[segments];
// first element starts with min
ranges[0] = Range.Make(min, min + range);
// each subsequent element is max
// of previous and max of previous
// plus the appropriate range
for (int i = 1; i < segments; i++)
{
ranges[i] = Range.Make(ranges[i - 1].Max, ranges[i - 1].Max + range);
}
// make last range slightly larger
// to maintain r.Min <= d < r.Max
ranges[ranges.Length - 1].Max += .01;
return(ranges);
}
/// <summary>
/// Rescales the input vector to the specified range.
/// <para>When <paramref name="minValue"/> and <paramref name="maxValue"/> are null, the vector instance min and max values are used instead.</para>
/// </summary>
/// <param name="v">Vector to rescale.</param>
/// <param name="min">New lower bound value.</param>
/// <param name="max">New upper bound value.</param>
/// <param name="minValue">Lower bound value prior to rescaling.</param>
/// <param name="maxValue">Upper bound value prior to rescaling.</param>
/// <returns></returns>
public static Vector Rescale(this Vector v, double min, double max, double?minValue = null, double?maxValue = null)
{
double min_tm1 = (minValue ?? v.Min());
double max_tm1 = (maxValue ?? v.Max());
Vector v_t = v.Each(d => ((max - min) * (d - min_tm1)) / (max_tm1 - min_tm1), true);
return(v_t);
}
/// <summary>
/// Computes the Normalized Root Mean Squared Error for the given inputs.
/// </summary>
/// <param name="y1">Predicted values.</param>
/// <param name="y2">Actual values.</param>
/// <returns>Double.</returns>
public static double ComputeNormRMSE(Vector y1, Vector y2)
{
return numl.Supervised.Score.ComputeRMSE(y1, y2) / (y1.Max() - y1.Min());
}
