# [R] Monte Carlo Simulation

Shane Phillips SPhillips at Lexington1.net
Sat Apr 16 00:23:05 CEST 2011

```I apologize for my last post.  here is the script I forgot to paste!

subject=1:1000
treat=rbinom(1*1000,1,.13)
gender=rbinom(1*1000,1,.5)
eth=runif(1*1000, min=1, max=4)
cogat=rnorm(1*1000, 100, 16)
map=rnorm(1*1000, 200, 9)
growth=0
simtest=data.frame (subject=subject, treat=treat, gender=gender, eth=round(eth,digits=0), cogat=round(cogat,digits=0),map=round(map,digits=0),growth)
simtest<-transform(simtest, growth=rnorm(1000,m=ifelse(treat==0,0.1,0.5),s=0.03))
simtest

Once again the issues are the correlations, the recoding of the categorical variable and the iterations.

Thanks to all who have helped so far!  You are all so smart!

S
________________________________________
From: Charles Annis, P.E. [charles.annis at statisticalengineering.com]
Sent: Friday, April 15, 2011 3:00 PM
To: Shane Phillips; r-help at r-project.org
Subject: RE: [R] Monte Carlo Simulation

What have you tried so far?

It is often helpful to begin with a much simpler problem, then add
complexity incrementally until you've constructed the desired model.

Best wishes.

Charles Annis, P.E.

Charles.Annis at StatisticalEngineering.com
561-352-9699
http://www.StatisticalEngineering.com

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Shane Phillips
Sent: Friday, April 15, 2011 2:50 PM
To: r-help at r-project.org
Subject: [R] Monte Carlo Simulation

Hello, R friends...

I am very new to R, and I need some help.  I am trying to construct a
simulation for my dissertation.

I need to create 1000 datasets of 1000 subjects with the following
variables...

Treatment variable - Drawn from a binomial distribution (1 run, prob=.13)
Covariate 1 - Drawn from a normal distribution (mean=100, sd=16)
Covariate 2 - Drawn from a normal distribution (mean=200, sd=9)
Covariates 1 and 2 need to be correlated (say, r=.80)
Covariate 3 - Drawn from a binomial distribution (1 run, prob=.5)
Covariate 4 - Drawn from a distribution of discrete variables where 1 has an
80% chance of being selected, 2  - 10%, 3 - 5% and 4 - 5%.  This variable
would need to be recoded into 4 binary variables.
Covariate 5 - Drawn from a normal distribution (mean=84, sd=2)
Covariate 6 - Drawn from a binomial distribution (1 run, prob=.15)
Covariate 6 needs to correlate with Covariate 2 (r=.70, or so)

I need each dataset saved as a new datafile with an iterative filename (e.g.
sample1, sample2, etc.).

Thanks!

Shane

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