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Re: multivariate uniform

To: Jewel Bright <jwlbright@yahoo.com>
Subject: Re: multivariate uniform
From: Tim Hesterberg <timh@insightful.com>
Date: 31 Aug 2006 11:18:05 -0700
Cc: s-news@lists.biostat.wustl.edu
In-reply-to: <20060811142708.34387.qmail@web38705.mail.mud.yahoo.com> (message from Jewel Bright on Fri, 11 Aug 2006 07:27:08 -0700 (PDT))
References: <20060811142708.34387.qmail@web38705.mail.mud.yahoo.com>
You can generate correlated multivariate normal with arbitrary correlations,
then transform each dimension from normal to uniform using pnorm.
Note that the correlation of the uniforms is somewhat smaller than
the correlation of the corresponding normal variates.  You can adjust the
correlation of the normals upward to get the output correlation you want.

More generally, look at the literature on copulas.  Alexander
McNeil has created a library with a variety of copulas
        http://www.math.ethz.ch/~mcneil/book/QRMlib.html
to accompany his book "Quantitative Risk Management: Concepts,
Techniques and Tools".

Tim Hesterberg

>Is their such a thing like multivariate UNIFORM distribution?
>  I mean the multivariate distrubution which is marginally uniform in  [0,1]
>  for all the components and having a prescribed correlation matrix 
> (non-diagonal)? 
>  How to generate such a thing? For a time being I would probably be satisfied 
> if all the cross correlations are identical.
>   
>  Thank you
>   
>  Jewel Bright

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