# How to sum two probability density functions?

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hello

I have created two probability density functions using this formula:

I would like to sum two of these pdfs and also substract both, but I have not idea how to do it.

Thanks in advance for your help

pd = fitdist(L1.Z(:),'Normal');

x_pdf = [min(L1.Z(:)):0.01:max(L1.Z(:))];

y = pdf(pd,x_pdf);

plot(x_pdf,y,'-')

##### 0 Comments

### Accepted Answer

ANKUR KUMAR
on 25 Feb 2019

"sum two of these pdfs and also substract both"?

Are you pretty sure to add the pdfs?

My suggestion is to first add data and then plot the pdf in the regular fashion.

If you facing some issues with plotting pdf, use join the tops of histograms of the data and convert y axis into percentage. This also gives you the probability of occurence of a number in your data.

##### 3 Comments

ANKUR KUMAR
on 25 Feb 2019

### More Answers (1)

Jules Ray
on 25 Feb 2019

Edited: Jules Ray
on 25 Feb 2019

##### 1 Comment

John D'Errico
on 25 Feb 2019

Please don't add answers just to ask another question.

Anyway, from reading your various comments, I don't think you understand what a PDF means. Forming the difference of two PDFs has almost no meaning that I can think of.

I think perhaps you want to form the sum and difference of two random variables? That is very, VERY different from forming the sum or difference of two PDFs. Perhaps that is what you mean.

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