Switch R Script from Non-Interactive to Interactive

Switch R script from non-interactive to interactive

Can you just fire up R and source the file instead?

R
source("script.R")

Run R interactively from Rscript

If I understand your question correctly, I was able to achieve this with littler, which I use in lieu of Rscript for scripting tasks that revolve around R. I'm running CentOS 7, and based on the code in your question it looks like you are on a Unix-like machine, so installing littler should not be an issue. For minimal reproducibility, I used the default shiny application and shiny-based Rmarkdown templates provided by RStudio, saving them as testapp (the project / application directory name) and testRMD.rmd, respectively. Then, I have the following scripts:

---

testapp.r

#!/usr/bin/env r

shiny::runApp(
  "~/tmp/delete/testapp",
  port = 7088, 
  launch.browser = TRUE,
  host = "127.0.0.1")

---

testRMD.r

#!/usr/bin/env r

rmarkdown::run(
  file = "testRMD.rmd",
  dir = "~/tmp/delete",
  shiny_args = list(
    port = 7088,
    launch.browser = TRUE,
    host = "127.0.0.1"))

---

Set the permissions for these files so they can be executed -

[nathan@nrussell R]$ chmod +x testapp.r testRMD.r

(chmod +u ... should suffice, but regardless...), and you should be all set to run them from your terminal, etc...

---

[nathan@nrussell R]$ ./testapp.r
Loading required package: shiny

Listening on http://127.0.0.1:7088

[nathan@nrussell R]$ ./testRMD.r
Loading required package: shiny

Listening on http://127.0.0.1:7088

---

There is some additional command line output for the Rmd file that I omitted, but I'm sure this could be suppressed easily if desired. Anyhow, this seems to be working properly - both the shiny application and Rmarkdown application are interactive, just as when launched from RStudio - but if you had something else in mind please clarify.

Switching a conditional based on whether R session is interactive or not

This?

if(base::interactive()){
        a <- 10
        b <- 6
    }else{
        args = commandArgs(trailingOnly = TRUE)
        a <- args[1]
        b <- args[2]
    }

How can I execute R one-liners from the terminal without exiting R?

With a function you can restart R automatically after using the parameters:

r() {

   # First execute commands when given
   if [ $# -gt 0 ]; then
      R --slave -e "$*"
   fi

   # Start R 
   R --slave

}    

After testing you can add this function to .bashrc.

I call the function r, but make sure r is not already used or reserved by your system.

You can call the function with r 1+1, r 1 + 1 of r "1*2".

Please note the quotes when you use "1*2".
Without quotes the shell will try to expand special characters, and will look for a file "1*2". It would be a lot worse with spaces, r 1 * 2 will replace * with a lot of filenames.

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