Read command line parameters from an R script

Question

In a R script I would like to apply various command line parameters.

The script runs on Windows.

I'm not able to find how to read parameters applied on the command line to R-script.

Any suggestions on how to do this?

Answer 1

Here's an example to explain :

Two files are created: example.bat and example.R

• example.bat:

  set R_Script="C:\Program Files\R-3.0.2\bin\RScript.exe"
  %R_Script% example.R 2018-01-28 example 100 > example.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 2018-01-28 example 100 < example.R > example.batch 2>&1

• example.R:

  options(echo=TRUE) # To see commands in output file
  args <- commandArgs(trailingOnly = TRUE)
  print(args)
  # trailingOnly=TRUE this means that only your arguments are returned, 

     # To check you can use:
     # print(commandArgs(trailingOnly=FALSE))

start_date <- as.Date(args[1])
name <- args[2]
n <- as.integer(args[3])
rm(args)

# Few computations:
x <- rnorm(n)
png(paste(name,".png",sep=""))
plot(start_date+(1L:n), x)
dev.off()

summary(x)

Now, save both files in the same directory and start example.bat. In the result you'll get:

• example.png with some plot
• example.batch with all that was done

You can add an environment variable %R_Script%:

"C:\Program Files\R-3.0.2\bin\RScript.exe"

And then use it in your batch scripts as %R_Script% <filename.r> <arguments>

Differences between RScript and Rterm:

• Rscript provides simpler syntax
• Rscript automatically chooses architecture on x64 (see R Installation and Administration, 2.6 Sub-architectures for details)
• Rscript needs options(echo=TRUE) in the .R file just in-case you want to write the commands to the output file