MATLAB Central Newsreader - How to fit normal distribution to histogram

How to fit normal distribution to histogram

Jamal Mohamed — Mon, 09 Nov 2009 09:06:02 -0500

Hi
How to fit normal(or any) distribution to histogram based its mode(peak) for image data ?

Re: How to fit normal distribution to histogram

Nasser M. Abbasi — Mon, 09 Nov 2009 09:31:47 -0500

"Jamal Mohamed" <in.jamal@yahoo.com> wrote in message
news:hd8m1p$rqq$1@fred.mathworks.com...
> Hi
> How to fit normal(or any) distribution to histogram based its mode(peak)
> for image data ?

normal dist. requires 2 parameters. mean and variance (or standard
deviation). can't just use the peak. If you have the data itself (the sample
from which you got the histogram from) then you can easily estimate these
from the sample data.

If you just have the plot itself, then you can find the mean (where the peak
is), for variance, find the area around the mean which is about 68% of total
area, this gives you 2 standard deviations as measured on the x-axis under
this area. But I am no expert on this so I could be off here.

(there is a statistic newgroup group btw).

--Nasser

Re: How to fit normal distribution to histogram

Frederic Moisy — Mon, 09 Nov 2009 10:00:20 -0500

Once the histogram of the image data is plotted, one easy way
to fit a normal distribution or other is to use the Ezyfit toolbox,
http://www.mathworks.com/matlabcentral/fileexchange/10176-ezyfit-2-30
Have a look to the example file
http://www.mathworks.com/matlabcentral/fx_files/10176/3/content/ezyfit/demo/html/efdemo.html
in which a normal fit is illustrated.
Frederic

"Jamal Mohamed" <in.jamal@yahoo.com> wrote in message <hd8m1p$rqq$1@fred.mathworks.com>...
> Hi
> How to fit normal(or any) distribution to histogram based its mode(peak) for image data ?

Re: How to fit normal distribution to histogram

Wayne King — Mon, 09 Nov 2009 11:45:03 -0500

"Frederic Moisy" <moisy@fast.u-psud.fr> wrote in message <hd8p7j$3hb$1@fred.mathworks.com>...
> Once the histogram of the image data is plotted, one easy way
> to fit a normal distribution or other is to use the Ezyfit toolbox,
> http://www.mathworks.com/matlabcentral/fileexchange/10176-ezyfit-2-30
> Have a look to the example file
> http://www.mathworks.com/matlabcentral/fx_files/10176/3/content/ezyfit/demo/html/efdemo.html
> in which a normal fit is illustrated.
> Frederic
>
>
> "Jamal Mohamed" <in.jamal@yahoo.com> wrote in message <hd8m1p$rqq$1@fred.mathworks.com>...
> > Hi
> > How to fit normal(or any) distribution to histogram based its mode(peak) for image data ?

If you have the statistics toolbox, there is also a histfit() function which provides density fits for a number of distributions.

Wayne