MathNet Matrix MapIndexInplace confusion about arguments

Question

The Matrix function MapIndexInplace is documented to take a Func (int, int, float, float). I don't understand what the second float value is. Can anyone explain?

Answer 1

The Func<int,int,float,float> delegate represents a function with two integers and a float as arguments and a float as return value. So the second float represents the function's return value.

MapIndexInplace will call the provided function of this type signature for each (or optionally each non-zero) matrix element with three arguments (index i, index j, current value v) and replace the matrix element value with the value returned by the called function.