[Bug-gsl] gsl_stats_sd_m ???

[Mehdi Esteghamatian]

Dear bug-gsl

Hope you are all fine.

This is Mehdi Stegamatian. I am student of "Artificial Intelligence" in
Shiraz University. It is about 6 mounts that I am using GSL. I found
something which appeared to me as a bug. GSL calculates standard deviation
of single number equal to nan! Which sounds a bit vired to me. I am not a
statistician but according to my knowledge the value is zero.

I included the sample code? Could you tell me what is going on?

Best Wishes,
Mehdi

///////////////////////////////////////////////////////////////////////////////
#include <stdio.h>
#include <gsl/gsl_statistics.h>
#include <gsl/gsl_randist.h>


int main()
{
        double darr[1][20];
        for (int i = 0; i < 20; i++)
        {
                for (int j = 0; j < 1; j++)
                {
                        darr[j][i] = i+j;
                }
        }

        double mean = gsl_stats_mean((const double *)(darr) + 10, 20, 1);
        double stddev = gsl_stats_sd_m((const double *)(darr) + 10, 20, 1, 
mean);

        printf("mean = %f\n", mean);
        printf("stddevvv = %f\n", stddev);
        return 0;
}
///////////////////////////////////////////////////////////////////////////////


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