colvec TestProcessing::accumarray(icolvec cf, colvec T, double nf, int p)
{
    /* ******* Description   *******

    here cf is the matrix of indices

    T is the values whose data is to be
    accumulted in the output array S.

    if T is not given (or is scaler)then accumarray simply converts
    to calculation of histogram of the input data

    nf is the the size of output Array

    nf >= max(cf)
    so pass the argument accordingly

    p is not used in the function

    ********************************/

    colvec S; // output Array

    S.set_size(int(nf)); // preallocate the output array

    for(int i = 0 ; i < (int)nf ; i++)
    {
        // find the indices in cf corresponding to 1 to nf
        // and store in unsigned integer array q1
        uvec q1 = find(cf == (i+1));
        vec q ;
        double sum1 = 0 ;

        if(!q1.is_empty())
        {
            q = T.elem(q1) ; // find the elements in T having indices in q1
            // make sure q1 is not empty

            sum1 = arma::sum(q); // calculate the sum and store in output array
            S(i) = sum1;
        }

        // if q1 is empty array just put 0 at that particular location
        else
        {
            S(i) = 0 ;
        }
    }
    return S;
}