std div

double std_div(vector<int>& vec, double mean)
{
    vector<double> holder;
    double holder_sum;
    double holder_div;
    double standard_div;

    //squares the value minus the mean
    for(int x=0; x < vec.size(); x++)
    {
        holder[x] = pow((vec[x] - mean), 2);
        cout << holder[x] << endl;
    }

    //sum of new vector
    for(int x=0; x < holder.size(); x++)
    {
        holder_sum += holder[x];
    }

    holder_div = holder_sum/holder.size();
    standard_div = sqrt(holder_div);

    return standard_div;
}