[R] R scripts and parameters

[Duncan Murdoch]

On 2/17/2009 10:55 AM, mauede at alice.it wrote:
> A couple of weeks ago I asked how it is possible to run an R script (not a function) passing some parameters.
> Someone suggested the function "commandArgs()".
> I read the on-line help and found no clarifying example. Therefore I do not know how to use it appropriately.
> I noticed this function returns the pathname of the R executable which is not what I need.
> 
> I meant to ask if it is possible to open an R session and launch a script passing parameters that the script can retrieve and use itself.
> Just like in C I can run a program and call it with  some arguments 
> 
>> Example_Prog A B C
>   
> The program "Example_Prog" can acess its own arguments through the data structures "argc" an "argv".
> 
> How can I launch an R script simulating the above mechanism ? 
> Shall I use source ("script-name") ?
> Where are the arguments to be passed, as part of the source call ?
> Is the function "commandArgs" to be places as one of the first code lines of the script in order to access its own arguments ?
> Is there any "commandArgs" usage example ?


Gabor gave you a solution from within R.  If you want to run a script 
from the command line, then use commandArgs(TRUE).  For example, put 
this into the file test.R:

commandArgs(TRUE)

(The TRUE says you only want to see the trailing arguments, not 
everything else on the command line.)

Then from the command line, do

Rscript test.R A B C

and you'll see the output

[1] "A" "B" "C"

Duncan Murdoch