/// <summary>
/// Return a function that computes the derivative of the gauss
/// function with mu = 0 and specified sigma.
/// </summary>
public static Func <float, float> GaussianDx(float sigma)
{
double s2 = sigma * sigma;
double a = -1.0 / (Constant.SqrtPiTimesTwo * s2 * sigma);
double b = -1.0 / (2.0 * s2);
return((float x) => (float)(a * x * Fun.Exp(b * (x * x))));
}
/// <summary>
/// Return a function that computes the partial derivative in Y of
/// the two-dimensional gauss function with mu = (0, 0) and
/// sigma = DiagonalMatrix(sigma).
/// </summary>
public static Func <float, float, float> Gaussian2Dy(float sigma)
{
double s2 = sigma * sigma;
double a = -1.0 / (Constant.PiTimesTwo * s2 * s2);
double b = -1.0 / (2.0 * s2);
return((float x, float y) =>
(float)(a * y * Fun.Exp(b * (x * x + y * y))));
}