How to create a function returning an array ?
@ Duncan, I have already used the syntax that you proposed before asking for help by writing something like
read_ts<-function(n,m,img) {
out<-.Fortran("read_ts",
as.integer(n),
as.integer(m),
img=as.single(rnorm(n*m)))
return(out$img)
alpha<-read_ts(n,m)
dim(alpha)<-c(n*m)
alpha<-t(alpha)
My worry with this syntax is that (i) the program is not very efficient because n and m are very big and these two additional instructions (dim(alpha)<-c(n*m and alpha<-t(alpha) can be skipped just by directly declaring img as an array in fortran instead of a vector and (ii) the syntax will become more complex dealing with a multidimensional array instead of a matrix as in this example. And this is why I'm looking for the correct instruction to declare img as an array instead of a vector. Armel -----Original Message----- From: Duncan Murdoch [mailto:murdoch.duncan at gmail.com] Sent: Friday, June 28, 2013 8:16 AM To: David Winsemius Cc: Kaptue Tchuente, Armel; r-help at r-project.org Subject: Re: [R] How to create a function returning an array ?
On 27/06/2013 11:38 PM, David Winsemius wrote:
On Jun 27, 2013, at 8:04 PM, Kaptue Tchuente, Armel wrote:
Hi there,
I would like to know how to change the line
"img=as.single(rnorm(m)))" such that instead of being a vector of
length m as it is now, img is an array of dimension c=(n,m,o) for
instance
---------------------------------
read_ts<-function(n,m,o,img) {
out<-.Fortran("read_ts",
as.integer(n),
as.integer(m),
as.integer(o),
img=as.single(rnorm(n)))
return(out$img)
------------------------------------------
Well, assuming that the 'out$img' object has a R-length of n*m*o , wouldn't if be simpler to just change the return call to:
In fact, out$img has a length of n, same as on input. .Fortran won't change the length of its arguments. Duncan Murdoch
return( array( out$img, dim=c(n,m,o) ) I don't think you wnat start naming your dimension vectors "c".