[R] for loop

[Brian Diggs]

On 10/14/2010 2:53 PM, li li wrote:
> Dear all,
>    I have a function f(x)  which return a list as result.
>
> $T1
> [1] 0.03376190
> $T2
> [1] 0.04725
> $T3
> [1] 0.3796071
> $T4
> [1] 0.3713452
> $T5
> [1] 0.4523651
> $T6
> [1] 0.4575873
>
>    I now find the result for a vector of x values at one time. I want to
> store the reuslt
> for each xi value in a column of a matrix
>
> x<- seq(0,1, by=0.1)
> result<- matrix(0, nrow=6, ncol=length(x))
>
> for (i in 1:length(x)){result[,i]<- f(x[i])}
>
> It is not working. Can some help me.
> Thank you very much!
>                          Hannah

In order to test my solution, I needed a function that returned 
something of the structure you had.

f <- function(x) {
	r <- as.list(rnorm(6))
	names(r) <- paste("T",1:6,sep="")
	r
}

Using that, you can replace the for loop with:

for (i in 1:length(x)){result[,i] <- unlist(f(x[i]))}

The problem is that f returns a list; you can only put a vector in part 
of a matrix.  unlist() takes care of that conversion.

-- 
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University