c++ armadillo modulus function

Question

What is the best way to perform modulus operator over a vector or matrix in c++ Armadillo?

The vector and matrix classes overload the % operator to perform element-wise multiplication. Trying to use it yields an invalid operands error. I was expecting that

uvec a = {0, 1, 2, 3};
uvec b = a % 2;
cout << "b" << endl;

would yield the following:

You'll have to do it element wise (e.g. in a loop). – πάντα ῥεῖ Dec 29 '14 at 09:31 — πάντα ῥεῖ, Dec 29 '14 at 09:31

score 4 · Accepted Answer · answered Jan 22 '15 at 17:07

4

Operator '%' is for element-wise matrix multiplication. You have to create your own function:

/**
 * Extend division reminder to vectors
 *
 * @param   a       Dividend 
 * @param   n       Divisor
 */
template<typename T>
T mod(T a, int n)
{
    return a - floor(a/n)*n;
}

answered Jan 22 '15 at 17:07

cecconeurale

108
6

Nice idea---you should make note that it will require the use of `arma::floor` and specify that it requires armadillo vector types, not `std::vector`s. – Brian Jan 23 '15 at 00:15

c++ armadillo modulus function

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