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Inverse Cumulative Distribution Function for a Custom PDF.

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Hello!
I'm looking for a function similar to norminv in wich you can sample data at the probability values in the vector p according to the normal distribution but I need to make it according to a custom probability distribution instead of the normal, always in the vector p but without the use of the original dataset wich generated the custom PDF.
Or in other words a icdf for a custom PDF function....Thanks!

Accepted Answer

Jeff Miller
Jeff Miller on 7 Mar 2020
If you have the custom PDF function (call it custPDF), then you can compute the custom CDF function something like this:
function p = custCDF(x)
p = integral(@custPDF,LowerBound,x); % Modify AbsTol and RelTol to suit your needs
end
where LowerBound is some minimal value for your custom distribution.
Then you should be able to get the inverse CDF with this:
function x = custiCDF(p)
x = fzero( @(x) custCDF(x)-p, [LowerBound,UpperBound] );
end
where UpperBound is a maximal value.
It might be pretty slow, but it should work.
  3 Comments
Emiliano Rosso
Emiliano Rosso on 8 Mar 2020
No,I misunderstood,I must call custiCDF for each one,
Thanks!

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