On Jul 31, 2015, at 6:36 PM, Christopher Kelvin via R-help wrote:
> Dear All,
> I am performing some simulations for a new model. I run about 10,000
> iterations with a sample of 50 datasets and this returns one set of 50
> simulated data.
>
> Now, what I need to obtain is 10 sets of the 50 simulated data out of the
> 10,000 iterations and not just only 1 set. The model is the Copas selection
> model for publication bias in Mete-analysis. Any one who knows this model has
> any suggestion for the improvement of my code is most welcome.
>
> Below is my code.
>
>
> Kind regards
>
>
> Chris Guure
> University of Ghana
>
>
>
>
> install.packages("msm")
> library(msm)
>
>
> rho1=-0.3; tua=0.020; n=50; d=-0.2; rr=10000; a=-1.3; b=0.06
> si<-rtnorm(n, mean=0, sd=1, lower=0, upper=0.2)# I used this to generate
> standard errors for each study
> set.seed(21111) ## I have stored the data and the output in this seed
>
> for( i in 1:rr){
>
> mu<-rnorm(n,d,tua^2) # prob. of each effect estimate
> rho<-si*rho1/sqrt(tua^2 + si^2) # estimate of the correlation coefficient
> mu0<- a + b/si # mean of the truncated normal model (Copas selection
> model)
> y1<-rnorm(mu,si^2) # observed effects zise
> z<-rnorm(mu0,1) # selection model
> rho2<-cor(y1, z)
>
> select<-pnorm((mu0 + rho*(y1-mu)/sqrt(tua^2 + si^2))/sqrt(1-rho^2))
> probselect<-ifelse(select<z, y1, NA)# the prob that the study is selected
>
> probselect
> data<-data.frame(probselect,si) # this contains both include and exclude
> data
> data
> data1<-data[complete.cases(data),] # Contains only the included data for
> analysis
> data1
>
>
> }
>
OK. The code runs without error. So .... what exactly is the problem? (I have
no experience with the Copas selection model if in fact that is what is being
exemplified.)
--
David Winsemius
Alameda, CA, USA
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