Create a matrix of random numbers with different distributions in each entry
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Pavel Penshin
on 23 Feb 2020
Commented: Thiago Henrique Gomes Lobato
on 23 Feb 2020
Say I have a matrix and I want to add an error to each of the elements, the error should be normally distributed around the element with variance of 0.1 of the value of the element.
That is how I implemented this:
A = [1 2 3 ; 4 5 6 ; 7 8 9]
sz=size(A);
sigma = 0.1*A;
err = zeros(sz);
for i=1:sz(1)
for j=1:sz(2)
pd = makedist('Normal','sigma',sigma(i,j));
err(i,j)=random(pd);
end
end
Result = A + err;
This is ok for 9 elemens but it is very time consuming when my matrix is 3000X3000
Is there any more efficient way to do so?
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Accepted Answer
Thiago Henrique Gomes Lobato
on 23 Feb 2020
Edited: Thiago Henrique Gomes Lobato
on 23 Feb 2020
Your code does basically this:
A = [1 2 3 ; 4 5 6 ; 7 8 9]
Result = A + randn(size(A))*0.1;
In your question however you seem to mean that the variance should be 0.1 of the element value, if this is the case do this:
A = [1 2 3 ; 4 5 6 ; 7 8 9]
Result = A.*(1+randn(size(A))*0.1)
I'm not sure what you actually want but those two solutions should solve it way faster than a loop
4 Comments
Thiago Henrique Gomes Lobato
on 23 Feb 2020
Yes. If you need the error matrix you can do it like this:
err = A.*randn(size(A))*0.1
Result = A+err;
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