Algorithm to create all possible combinations

Question

I\'m writing a spares grid code and need to combine N 1-dimensional grid points (written in vector form) into the an array of all possible points. For example one can mix two ve

Answer 1

I don't know Fortran, but since you say you can't find the underlying algorithm I'm assuming you will be able to write this yourself once you know the algorithm. It's quite easy actually. The pseudocode would be something like this (assuming there are no duplicates):

index = 0   ! or 1
for each element in first vector
    for each element in second vector
        matrix(index,1) = current element of first vector
        matrix(index,2) = current element of second vector
        index = index + 1
    end for
end for

This should give you a matrix similar to the one you would get using combvec. There are probably more efficient ways to do this, but as I don't know the details of Fortran I can't help you there unfortunately. In Matlab you would of course vectorize this.

Good luck =)