I have defined a custom function, like this:
my.fun = function() {
for (i in 1:1000) {
...
for (j in 1:20) {
...
}
}
return(output)
}
which returns an output matrix, output
, composed by 1000 rows and 20 columns.
What I need to do is to repeat the function say 5 times and to store the five output
results into a brand new matrix, say final
, but without using another for-loop (this for making the code clearer, and also because in a second moment I would like to try to parallelize these additional 5 repetitions).
Hence final
should be a matrix with 5000 rows and 20 columns (the rationale behind these 5 repetitions is that within the two for-loops I use, among other functions, sample
).
I tried to use final <- replicate(5, my.fun())
, which correctly computes the five replications, but then I have to "manually" put the elements into a brand new 5000 x 20 matrix.. is there a more elgant way to do so? (maybe using sapply()
?). Many thanks
replicate() function in R Programming Language is used to evaluate an expression N number of times repeatedly.
Repeat Function in R:The Repeat Function(loop) in R executes a same block of code iteratively until a stop condition is met. repeat loop in R, is similar to while and for loop, it will execute a block of commands repeatedly till break.
Repeat loop in R is used to iterate over a block of code multiple number of times.
As is stands you probably have an array with three dimensions. If you wanted to have a list you would have added simplify=FALSE. Try this:
do.call( rbind, replicate(5, my.fun(), simplify=FALSE ) )
Or you can use aperm
in the case where "final" is still an array:
fun <- function() matrix(1:10, 2,5)
final <- replicate( 2, fun() )
> final
, , 1
[,1] [,2] [,3] [,4] [,5]
[1,] 1 3 5 7 9
[2,] 2 4 6 8 10
, , 2
[,1] [,2] [,3] [,4] [,5]
[1,] 1 3 5 7 9
[2,] 2 4 6 8 10
> t( matrix(aperm(final, c(2,1,3)), 5,4) )
[,1] [,2] [,3] [,4] [,5]
[1,] 1 3 5 7 9
[2,] 2 4 6 8 10
[3,] 1 3 5 7 9
[4,] 2 4 6 8 10
There may be more economical matrix operations. I just haven't discovered one yet.
If you replace replicate
with rlply from the plyr
package, you can use do.call
with rbind
:
library(plyr)
do.call(rbind, rlply(5, my.fun()))
If you'd rather not rely on the plyr
package, you can always do:
do.call(rbind, lapply(1:5, function(i) my.fun()))
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