No suitable user-defined conversion from "const arma::subview_col<double>" to "const arma::uvec" exists

  armadillo, c++

I have some trouble in my code with Armadillo. I’m trying to create a subvector and submatrix from another one through a sliding windows (called epoch in the code). Here is my code:

void trainModel(const mat& X, const uvec& y){
// ...
// Creating a new X, y depending on epochs
    mat XBis(numOfEpochs, X.n_cols);
    uvec yBis(numOfEpochs);
    unsigned long start = 0, end = 0;
    for (unsigned long i = 0; i < numOfEpochs; i++)
        start = i * m_epochShift;// start of the subvec
        end = ((i * m_epochShift) + (m_epochSize - 1) >= m_numOfSamples ? m_numOfSamples - 1 : (i * m_epochShift) + (m_epochSize - 1)); // check if we reach the end of the vector, to avoid acessing unallocated area
        // get the class of the epoch
        yBis[i] = determineClass(y.subvec(start, end), 
                                 (i==0)?0:y((i * m_epochShift)-1)); // getting the previous data, if it's the begining, it sends zero (not a class id)

        for (unsigned int j = 0; j < m_numFeatures; j++)
            switch (m_inputModels[j])
                case InputDistribution::GAUSS:
                    XBis(i, j) = mean(X.col(j).subvec(start, end));
                case InputDistribution::BERNOUILLI:
                    XBis(i, j) = determineClass(X.col(j).subvec(start, end), (i == 0) ? 0 : X.col(j)((i * m_epochShift) - 1));
                    throw exception("Unknow distribution");

NB : m_numFeatures = X.n_cols and m_numOfSamples = X.n_rows. X and y have the same number of rows.
Here is the prototype of my determineClass function:

unsigned long determineClass(const uvec& y, unsigned long previousValue)

I get the error message inside the case InputDistribution::BERNOUILLI. I understand what it is telling me, the subvec function gives a const arma::subview_col<double> object and my function is expecting a const arma::uvec. But I don’t get why I don’t have the error for the yBis[i] = determineClass(...) part (I tried and it works for this one). How should I do to get a subvector from a matrix?

I hope I didn’t miss important information,
thanks in advance for your help.

Source: Windows Questions C++