On Apr 1, 2010, at 12:16 PM, Greg Gilbert wrote:
I have code that creates the same matrices , "a" and "b". The code
creating
"a" is not in a function and the code creating "b" is in a function.
I would
like to do operations on "b" like I can on "a", however I can't
figure out
how I can return a matrix (or data frame) from a function. Thanks
for your
help!
r <- 5; c <- 5
a <- matrix(NA,nrow=5, ncol=5)
for(i in 1:r) {
+ for (j in 1:c) {
+ if(i==j) a[i, j] <- i
+ }
+ }
diag(a)
[1] 1 2 3 4 5
data.out <- function(r, c) {
+ b <- matrix(NA,nrow=r, ncol=c)
+ for(i in 1:r) {
+ for (j in 1:c) {
+ if(i==j) b[i, j] <- i
+ }
+ }
+ }
data.out(5, 5)
diag(b)
Error in diag(b) : object 'b' not found
The "b" object only existed while the function was being processed. At
the conclusion of the function's activities the b object did not get
returned as the result . Had you returned "b" or made it the last
object evaluated (inside the function), the results of data.out(5,5)
it would have still been accessible. Try this instead
data.out <- function(r, c) {
b <- matrix(NA,nrow=r, ncol=c)
for(i in 1:r) {
for (j in 1:c) {
if(i==j) b[i, j] <- i
}
}
b} # or equivalently return(b)
> diag(data.out(5,5))
[1] 1 2 3 4 5
--
David
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