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

Answer

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(commandsArgs(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 result you got:

• example.png with some plot
• exmpl.batch with all what was done

Just to add - you could add environment variable %R_Script%:

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

and use it in your batch scripts as %R_Script% .......

Differences between RScript and Rterm:

• Rscript has simpler syntax
• Rscript by-self choose architecture on x64 (see R Installation and Administration, 2.6 Sub-architectures for details)
• Rscript need options(echo=TRUE) in R-file if you want write commands to output file