How can I read command line parameters from an R script?
Dirk's answer here is everything you need. Here's a minimal reproducible example.
I made two files: exmpl.bat
and exmpl.R
.
exmpl.bat
:set R_Script="C:\Program Files\R-3.0.2\bin\RScript.exe" %R_Script% exmpl.R 2010-01-28 example 100 > exmpl.batch 2>&1
Alternatively, using
Rterm.exe
:set R_TERM="C:\Program Files\R-3.0.2\bin\i386\Rterm.exe" %R_TERM% --no-restore --no-save --args 2010-01-28 example 100 < exmpl.R > exmpl.batch 2>&1
exmpl.R
:options(echo=TRUE) # if you want see commands in output file args <- commandArgs(trailingOnly = TRUE) print(args) # trailingOnly=TRUE means that only your arguments are returned, check: # print(commandArgs(trailingOnly=FALSE)) start_date <- as.Date(args[1]) name <- args[2] n <- as.integer(args[3]) rm(args) # Some computations: x <- rnorm(n) png(paste(name,".png",sep="")) plot(start_date+(1L:n), x) dev.off() summary(x)
Save both files in the same directory and start exmpl.bat
. In the result you'll get:
example.png
with some plotexmpl.batch
with all that was done
You could also add an environment variable %R_Script%
:
"C:\Program Files\R-3.0.2\bin\RScript.exe"
and use it in your batch scripts as %R_Script% <filename.r> <arguments>
Differences between RScript
and Rterm
:
Rscript
has simpler syntaxRscript
automatically chooses architecture on x64 (see R Installation and Administration, 2.6 Sub-architectures for details)Rscript
needsoptions(echo=TRUE)
in the .R file if you want to write the commands to the output file
A few points:
Command-line parameters are accessible via
commandArgs()
, so seehelp(commandArgs)
for an overview.You can use
Rscript.exe
on all platforms, including Windows. It will supportcommandArgs()
. littler could be ported to Windows but lives right now only on OS X and Linux.There are two add-on packages on CRAN -- getopt and optparse -- which were both written for command-line parsing.
Edit in Nov 2015: New alternatives have appeared and I wholeheartedly recommend docopt.