/// <inheritdoc/>
public double value(double[] x)
{
int n = x.Length;
// delegate computation to underlying function
DerivativeStructure[] dsX = new DerivativeStructure[n];
for (int i = 0; i < n; ++i)
{
if (i == k)
{
dsX[i] = new DerivativeStructure(1, 1, 0, x[i]);
}
else
{
dsX[i] = new DerivativeStructure(1, 1, x[i]);
}
}
DerivativeStructure y = f.value(dsX);
// extract partial derivative
return(y.getPartialDerivative(1));
}
/// <inheritdoc/>
public double[] value(double[] x)
{
int n = x.Length;
// delegate computation to underlying function
DerivativeStructure[] dsX = new DerivativeStructure[n];
for (int i = 0; i < n; ++i)
{
dsX[i] = new DerivativeStructure(n, 1, i, x[i]);
}
DerivativeStructure y = f.value(dsX);
// extract gradient
double[] gradient = new double[n];
int[] orders = new int[n];
for (int i = 0; i < n; ++i)
{
orders[i] = 1;
gradient[i] = y.getPartialDerivative(orders);
orders[i] = 0;
}
return(gradient);
}