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[Help-gsl] gsl_ran_gaussian giving non-zero mean !
From: |
Sumesh P.T. |
Subject: |
[Help-gsl] gsl_ran_gaussian giving non-zero mean ! |
Date: |
Tue, 13 Oct 2009 18:12:48 +0530 |
I am using gsl_ran_gaussian to generate a random number distribution
with a specified standard deviation. Surprisingly the mean of the
distribution is not zero !!! Can it be possible? The mean does not
fluctuate around zero, but rather tends to be with a positive
value....Is this expected? or my interpretation is wrong? Has anyone
tried this?
I am giving my program and result here:
###########Program##########################3
#include <stdlib.h>
#include <math.h>
#include "concen.h"
#include <gsl/gsl_errno.h>
#include <gsl/gsl_matrix.h>
#include <gsl/gsl_odeiv.h>
#include <gsl/gsl_rng.h>
#include <gsl/gsl_randist.h>
int main() {
double y,sum=0.;
const gsl_rng_type * R;
gsl_rng * r;
gsl_rng_env_setup();
R = gsl_rng_default;
r = gsl_rng_alloc (R);
for(int i=1;i<=10000;i++) {
y = gsl_ran_gaussian(r,1.);
sum=sum+y;
printf("%f, %f, %f ,\n",y,sum,sum/i);
}
}
##############################################
##############################################
Last 10 values after calling it 10000 times
------------------------------------------------------
random sum mean
0.806397, 130.966701, 0.013108 ,
-0.096531, 130.870170, 0.013097 ,
-0.440024, 130.430146, 0.013052 ,
0.482622, 130.912768, 0.013099 ,
0.798685, 131.711453, 0.013178 ,
1.904331, 133.615784, 0.013367 ,
0.124113, 133.739897, 0.013378 ,
-0.728447, 133.011450, 0.013304 ,
-1.790865, 131.220585, 0.013123 ,
-2.349805, 128.870779, 0.012887 ,
Both sum and mean are positive values with no fluctuations around
zero! Is not that surprising?
Thanks,
sumesh
- [Help-gsl] gsl_ran_gaussian giving non-zero mean !,
Sumesh P.T. <=