How can I read command line parameters from an R script?

monch1962 picture monch1962 · Jan 28, 2010 · Viewed 173k times · Source

I've got a R script for which I'd like to be able to supply several command-line parameters (rather than hardcode parameter values in the code itself). The script runs on Windows.

I can't find info on how to read parameters supplied on the command-line into my R script. I'd be surprised if it can't be done, so maybe I'm just not using the best keywords in my Google search...

Any pointers or recommendations?

Answer

Marek picture Marek · Jan 28, 2010

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 plot
  • exmpl.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: