Question

I have an R script that outputs TRUE or FALSE. In R, it’s using a bona fide T/F data type, but when I echo its return value to bash, it seems to be a string, saying:

"[1] TRUE"

or

"[1] FALSE"

They are both preceded by [1]. Neither is [0], that is not a typo. Anyway, the result of this is what when I try to test on the output of this Rscript to run a subsequent script, I have to do string comparison to "[1] TRUE" as below, instead of comparing to "TRUE" or "1" which feels cleaner and better.

A=$(Rscript ~/MyR.r)
echo $A
if [ "$A" == "[1] TRUE" ]; then
    bash SecondScript.sh
fi

How can I make R either output a true Boolean, or Bash accept the output string and convert it to 0/1 for comparison? That is, I’d rather test for…

if [ $A == TRUE ];

than

if [ "$A" == "[1] TRUE" ];

Is that possible, or should I be happy with this, how it is, which works?

*** UPDATE ***

Here’s the minimalized version of the Rscript that generates this…

myinput <- TRUE #or FALSE

FunctionName <- function(test){
  if (test == TRUE){
    val <- TRUE
  } else {
    val <- FALSE
  }
  return(val)
}

FunctionName(myinput)

Answer 1

Instead of using either print() or the implicit print()-ing that occurs when an object name is offered to the R interpreter, you should be using cat() which will not prepend the “[1] ” in front of either TRUE or FALSE. If you want 0/1, then use cat(as.numeric(.)). Try this instead:

myinput <- TRUE #or FALSE
FunctionName <- function(test){
   if (test == TRUE){
              val <- TRUE
                    } else {
              val <- FALSE
            }
   cat(as.numeric(val))
}
FunctionName(myinput)

If you needed that value for further processing you could also use this:

cat(as.numeric(val)); invisible(val)