R help - Apr 2011 - 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.).

Please help!

Thanks!

Shane

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.). 

Please help!

Thanks!

Shane

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Hi Shane,
See ?rbinom, ?rnorm, ?mvrnorm (in the MASS package), ?sample, ?for and
?write.table

Best,
Ista

On Fri, Apr 15, 2011 at 2:49 PM, Shane Phillips
<SPhillips at lexington1.net> wrote:
> 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.).
>
> Please help!
>
> Thanks!
>
> Shane
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org

The filenames can be done within a loop, like this:

for (id in 1:1000) {
  ## the filename
  fname <- paste('sample',
formatC(id,width=4,flag='0'),'.tsv',sep='')

   ## more stuff
}


-Don

-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





-----Original Message-----
From: Shane Phillips <SPhillips at Lexington1.net>
Date: Fri, 15 Apr 2011 11:49:48 -0700
To: "r-help at r-project.org" <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.).
>
>Please help!
>
>Thanks!
>
>Shane
>
>______________________________________________
>R-help at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.