[R] repeating a function and combining the results

[Bert Gunter]

Arun has given you a number of ways to do what you (seem to) want. If
this is fast enough, then you're done.

If not, then the key to speeding things up is to do things
differently. Note that a 1 x 9 matrix is a just a vector. Since each
element of the vector is a "different computation", apparently
independent of the others, what you want to do is vectorize the
computation to calculate the whole column, not just a single value.
Whether and how you do this depends on the specific nature of the
computation, of course.

Cheers,
Bert

On Mon, Dec 2, 2013 at 9:52 PM, arun <smartpink111 at yahoo.com> wrote:
> HI,
> May be this helps:
>
> example <- function(X,n){
> lst1 <- list()
> for(i in 1:n){
> cell1 <- sample(X,1)
> cell2 <- sample(X,1)
> table1 <- cbind(cell1,cell2)
> lst1[[i]] <- table1
> }
> do.call(rbind,lst1)
> }
>
> #or
>
>
> example1 <- function(X,n){
> table1 <- vector()
> for(i in 1:n){
> cell1 <- sample(X,1)
> cell2 <- sample(X,1)
> table1 <- rbind(table1,c(cell1=cell1,cell2=cell2))
> }
> table1
> }
>
> set.seed(24)
> res1 <- example(1:10,3)
>
> set.seed(24)
> res2 <- example1(1:10,3)
>  identical(res1,res2)
> #[1] TRUE
>
> #or
>  set.seed(24)
> res3 <- t(replicate(3,c(sample(10,1),sample(10,1))))
> colnames(res3) <- colnames(res2)
>  identical(res2,res3)
> #[1] TRUE
>
>
>
> A.K.
>
>
> I have written a lengthy function that conducts a simulated
> mark/recapture study using random numbers. The output from the program
> is a matrix with a single row and nine columns (each column contains the results of a different calculation). Because of the random numbers,
> each time that I run the program, I get a different result. I need to be able to run it a fixed number of times and have all the results in a
> single matrix. I have written a second function that repeats the first
> and combines the results into a single table. Each time that I use that
> line of code, it reruns the first program, generating a new row of data, and combines it with the previous rows. How do I repeat that line 100
> times so that I get a table will 100 rows of data (each row should be
> unique).
>
> Here is a simplistic example of what I have so far
>
> example <- function(X){
> cell1 <- sample(X,1)
> cell2 <- sample(X,1)
> table1 <- cbind(cell1,cell2)}
> table2 <- example(1:10)
> example2 <- function(test){rbind(table2,example(1:10))}
> table2 <- example2(table2)
>
> Every time that you enter the line table2 <- example2(table2)
>  it will add a new line of data to the table, but I don't want to have
> to enter that line 100 times. So how do I get that line/function to
> repeat a specified number of times?
>
>
> I have tried both repeat and replicate and neither of them worked.
>
> Thanks for the help
>
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> and provide commented, minimal, self-contained, reproducible code.



-- 

Bert Gunter
Genentech Nonclinical Biostatistics

(650) 467-7374