[R] simulating binary variables
Jonathan Baron
baron at cattell.psych.upenn.edu
Fri Aug 9 16:25:47 CEST 2002
On 08/09/02 13:28, laura at bayesian-bay.freeserve.co.uk wrote:
>I am wanting to simulate a data set consisting of a Y variable
and several X variables, all either binary or discrete. I am
wondering how to go about doing this and have failed to find
anything about this in the R -help.
Try runif() in the base package. It generates random numbers
from a uniform distribution. So, for example, if you want a
binary variable with an expectation of .75, and 1000
observations, say:
runif(1000)<=.75
Or, if you want to see the numbers right away:
(runif(1000)<=.75)+0
To generate a factor with several levels, you can apply cut() to
runif(). That may be sufficient, but note that factors are
"categorical variables."
Of course, you assign these to variables, e.g.,
x1 <- runif(1000)<=.75
and then use these in your model.
Jon
--
Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron
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