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eren eren
eren eren 2012-12-6
I want to generate random numbers. But i want it like this. for example i want to generate random numbers for The gamma distribution coefficient of skewness 2.
How can i do this?

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José-Luis
José-Luis 2012-12-6
编辑：José-Luis 2012-12-6
doc gamrnd
The skewness is a function of one of the two parameters of the distribution, that you can set as you see fit. You just need to set it so the skewness is two (look at the wikipedia article on the gamma distribution).
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José-Luis
José-Luis 2012-12-13
编辑：José-Luis 2012-12-13
From one of your comments.
When you do this:
i write this on matlab skewness = 2; scale = 1; shape = 2./sqrt(skewness); x=gamrnd(shape,scale) s=skewness(x)
Skewness becomes a variable, and overshadows the built-in skewness function in Matlab. It is good practice not to do that, as problems as the one got might pop-up (you think you are calling a function but you are in fact trying to access a variable).
After clearing your work space to make sure there is no variable called skweness in it, do this instead:
ske = 2;
sca = 1;
shap = 1/sqrt(2);
x = gamrnd(shap,sca,[1000 1]);
your_skew = skewness(x);
Please accept an answer if it helped you.
eren eren
eren eren 2012-12-13
yes it is working. can i use this, beta, chi squre etc. distributions?

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Jonathan Sullivan
Jonathan Sullivan 2012-12-6
skewness is simple 2 divided by the square root of the shape parameter for gamma distributions. Here's an example.
skewness = 2;
scale = 1;
shape = 2./sqrt(skewness);
gamrnd(shape,scale)
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eren eren
eren eren 2012-12-13
i write this on matlab skewness = 2; scale = 1; shape = 2./sqrt(skewness); x=gamrnd(shape,scale) s=skewness(x)
and error is;
??? Attempted to access skewness(0.412164); index must be a positive integer or logical.
José-Luis
José-Luis 2012-12-13
Please see the comment to my original answer.

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