[R] Storing output vector form a loop as a matrix

[David Barron]

I'm not sure I've completely understood this, but would this do what you want:


for (i in 1:N){

aa <- sample(a, replace=TRUE)

c <-data.frame(b,aa)

output <- by(c, aa, function(x) sum(x$b))

output.matrix[,i] <- as.vector(output)
}



On 17/06/07, Economics Guy <economics.guy at gmail.com> wrote:
> Based on help files and searching the archives and help from the listserv I
> have managed to build my monte carlo program.
>
> However I cannot get the proper syntax for running the loop and storing the
> output of each loop (which is a vector) into a matrix.
>
> I took out some of the crazy code I was writing, but here is what I have:
>
> --------------------
>
> rm(list = ls(all = TRUE))
> # removes everything
>
> a <-c("A","C","B","A","B","C")
>
> b <-c(10,20,30,40,50,60)
>
> c <-data.frame(a,b)
>
> N=10 #Number of Loops
>
> output.matrix <- matrix(0.0,3,N)
>
> #I need to START LOOP HERE
>
> a <- sample(a, replace=TRUE)
>
> c <-data.frame(b,a)
>
> output.vector <- by(c, a, function(x) sum(x$b))
>
> output.vector <- as.vector(output)
>
> output.vector <- data.frame(output)
>
> #END LOOP here
>
>
> --------------------------
>
> What I would like to have at the end is the "output.matrix" contain as a
> column the  "output.vector" from  each iteration. The actual data frame I
> will be running has 60,000 observations and I am going to run 20000
> iterations so speed is important too.
>
> Thanks so much
>
> EG
>
>         [[alternative HTML version deleted]]
>
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>


-- 
=================================
David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP