passing parameters to an R script
On Sat, Jan 3, 2009 at 1:32 PM, <mauede at alice.it> wrote:
I knowf R functions ca be called passing some parameters. My first question is: how are parameters passed to R functions ? Browsing through R archives I found an answer confirming taht parameters can be passed to the called function by value. I wonder whether passing the parameter address is possible somehow to allow the function to actually change its value.
Normally this is done by passing back the modified variable as the return value:
a <- 0 fn <- function(x) x+1 a <- fn(a) a
[1] 1 Another possibility is to use environments. In the following function fn increments component x of environment e:
e <- new.env() e$x <- 0 fn <- function(e) e$x <- e$x + 1 fn(e) e$x
[1] 1 You can use parent.frame() to refer to the calling environment. ?parent.frame It may be that e above is really best viewed as an object in object oriented programming. In that case the proto package implements such a model in R and R.oo implements a different oo model.
My second question is about running R scripts with parameters. Something similar to the s/w device (argc, argv) which is used to run a C program with initial parameters. Is this possible at all ?
?commandArgs
Thank you very much.
Maura
tutti i telefonini TIM!
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