[R] Command Line Expressions

[Barry Rowlingson]

Pingping Zheng wrote:

> Is it possible to run R in command line to evalute R expressions
> and return results to stdout, something like
> 
> Or do a simple calculation
>  >R CMD -e "sin(1.2)"
>  >0.932039

Yes, with a bit of trickery!

  R on Unix will read from standard in, so you need to feed your R from 
stdin - typically use 'echo' to send a string to stdin.

  You'll also want to use --slave to stop all of R's startup messages, 
and probably --no-save as well.

  Also, you may need to cat() the expression:

$ echo "cat(sin(1.2))" | R --no-save --slave
0.932039

  ...otherwise you get R's default print labelling:

$echo "sin(1.2)" | R --no-save --slave
[1] 0.932039


Baz