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Re: st: simulating data for logistic regression: translating R to Stata


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: simulating data for logistic regression: translating R to Stata
Date   Tue, 3 Jun 2008 21:30:59 +0100 (BST)

--- Michael McCulloch <mm@pinest.org> wrote:
> For the command below which creates a variable with mean 200 and
> sd==25,
> gen chol = 200+25 * invnorm(uniform())
> 
> what does the "invnorm(uniform()))" do?
> I know the uniform() draws a random number with mean 0 and sd==1, but
> 
> what about the "invnorm" part?

-invnorm()- is an old name for -invnormal()- which I sometimes still
use because I forget the new name. To quote the helpfile: it "returns
the inverse cumulative standard normal distribution: if normal(z) = p,
then invnormal(p) = z." So this turns the draws from the uniform
distribution into draws from a standard normal distribution, than
multiplying by 25 leads to a standard dev. of 25 and adding 200 leads
to a mean of 200.

-- Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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