Matrix vector product

I have the values of a matrix in a vector:

vector<int> values;

and I want to multiply this "matrix" by a vector, I tried this:

 vector<float> Matrix::operator*(vector<float> vec) {
    vector<float> c;
    c.resize(vec.size());
    int counter = 0;

    float i = 0;
    while (i <= float(m_valor.size() / vec.size())) {
        for (int j = 0; j < vec.size(); j++) {
            if (counter > m_valor.size() - 1) {
                break;
            }
            c[j] = (m_valor[counter] * vec[j]) + c[j];
            counter++;
        }
        i++;
    }
    return c;
}

But the result seems not correct