# [R] Simulation over data repeatedly for four loops

R. Michael Weylandt michael.weylandt at gmail.com
Sun Nov 13 22:27:26 CET 2011

```Perhaps you might want to abstract your code a bit and try something like:

X = rnorm(500) # Some Data
replicate(1e4, mean(sample(X, 500, replace = T)))

Obviously you can set up a loop over your data sets as needed.

Michael

On Sat, Nov 12, 2011 at 6:46 PM, Francesca <francesca.pancotto at gmail.com> wrote:
> Dear Contributors,
>
> I am trying to perform a simulation over sample data,
>
> but I need to reproduce the same simulation over 4 groups of data. My
> ability with for loop is null, in particular related
>
> to dimensions as I always get, no matter what I try,
>
> "number of items to replace is not a multiple of replacement length"
>
>
> This is what I intend to do: replicate this operation for
>
> four times, where the index for the four groups is in the
>
> part of the code: datiPc[[1]][,2].
>
> I have to replicate the following code 4 times, where the
>
> changing part is in the data from which I pick the sample,
>
> the data that are stored in datiPc[[1]][,2].
>
> If I had to use data for the four samples, I would substitute the 1 with a
> j and replicate a loop four times, but it never worked.
>
>
> My desired final outcome is a matrix with 10000 observations for each
> couple of extracted samples, i.e. 8 columns of 10000 observations of means.
>
>
>
> db<-c()
>
> # Estrazione dei campioni dai dati di PGG e TRUST
>
> estr1 <- c();
>
>    estr2 <- c();
>
>    m1<-c()
>
>    m2<-c()
>
>       tmp1<- data1[[1]][,2];
>
>      tmp2<- data2[[2]][,2];
>
>        for(i in 1:100){
>
> estr1<-sample(tmp1, 1000, replace = TRUE)
>
>        estr2<-sample(tmp2, 1000, replace = TRUE)
>
>
>        m1[i]<-mean(estr1,na.rm=TRUE)
>
>        m2[i]<-mean(estr2,na.rm=TRUE)
>
> }
>
> db<-data.frame(cbind(m1,m2))
> Best Regards
>
> --
>
> Francesca
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>
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