How do I claim this set of data follows an exponential distribution?

Asked Mar 07 '17 at 15:23

Active Mar 07 '17 at 15:23

Viewed 245 times

I have a set of data that has following histogram:

I would like to guess it follows an exponential distribution. So I did some goodness of fit using KS test with MATLAB like following:

%% first load the data
fileID = fopen('data.dat','r')
dct= fread(fileID,'float');
fclose(fileID);

%% do distribution fitting
pd = fitdist(dct(:),'Exponential');

%% do ks test
test_cdf = makedist('exp', 'mu',  pd.mu);
[h, p] = kstest(dct(:), 'CDF', test_cdf);

However, I got

which means the hypothesis that my data follows an exponential is rejected.

I am wondering where I got wrong? Or how can I confirm the data I have follows an exponential distribution? Thanks a lot. I am attaching the original data here.

data.dat

asked Mar 07 '17 at 15:23

Nick X Tsui

1

Try histogram(log10(dct),100). There are a whole bunch of values around 4e-11, 6e-10, 2.5e-9 etc... It doesn't look exponential. – Matthew Gunn Mar 07 '17 at 16:16
@MatthewGunn I seem not to have histogram() function built in my MATLAB. Mine is 2014. – Nick X Tsui Mar 07 '17 at 18:44
use hist then. Some other ideas: (1) x = sort(dct) and then inspect x by hand. (2) A tool for comparing distributions you should be aware of is qqplot. – Matthew Gunn Mar 07 '17 at 19:07

How do I claim this set of data follows an exponential distribution?

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