From: Shane Phillips <SPhillips_at_Lexington1.net>

Date: Sun, 01 May 2011 00:33:41 -0400

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. Received on Sun 01 May 2011 - 06:00:08 GMT

Date: Sun, 01 May 2011 00:33:41 -0400

Please help...

Shane

Script follows...

#Number the subjects

subject=1:1000

#Assign a treatment condition from a binomial distribution with a probability of 0.13

treat=rbinom(1*1000,1,.13)

#Assign a lunch status condition froma binomial distribution with a probability of 0.35

lunch=rbinom(1*1000,1,.35)

#Generate age in months from a random normal distribution with mean of 87 and sd of 2

age=rnorm(1000,87,2)

#invoke the MASS package

require(MASS)

#Establish the covariance matrix for MAP, ITBS and CogAT scores

sigma <- matrix(c(1, 0.84, 0.59, 0.84, 1, 0.56, 0.59, 0.56, 1), ncol = 3)

#Establish MAP as a random normal variable with mean of 200 and sd of 9

map <- rnorm(1000, 200, 9)

#Establish ITBS as a random normal variable with mean of 175 and sd of 15

itbs <- rnorm(1000, 175, 15)

#Establish CogAT as a random normal variable with mean of 100 and sd of 16

cogat<-rnorm(1000,100,16)

#Create a dataframe of MAP, ITBS, and CogAT

data <- data.frame(map, itbs, cogat)

#Draw from the multivariate distribution defined by MAP, ITBS, and CogAT means and the covariance matrix

sim <- mvrnorm(1000, mu=mean(data), sigma, empirical=FALSE)

#Set growth at 0

growth=0

#Combine elements into a single dataset

simtest=data.frame (subject=subject, treat=treat,lunch, age=round(age,0),round(sim,0),growth)

#Set mean growth by treatment condition with treatd subjects having a mean growth of 1.5 and non-treated having a mean growth of 0.1

simtest<-transform(simtest, growth=rnorm(1000,m=ifelse(treat==0,0.1,1.5),s=1))
simtest

cor (simtest)

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