Can the print() command in R be quieted?

Question

In R some functions can print information and return values, can the print be silenced?

For example:

print.and.return <- function() {
  print("foo")
  return("bar")
}

returns

> print.and.return()
[1] "foo"
[1] "bar"
> 

I can store the return like:

> z <- print.and.return()
[1] "foo"
> z
[1] "bar"
> 

Can I suppress the print of "foo"?

Answer 1

?capture.output

Answer 2

If you absolutely need the side effect of printing in your own functions, why not make it an option?

print.and.return <- function(..., verbose=TRUE) {
  if (verbose) 
    print("foo")
  return("bar")
}


> print.and.return()
[1] "foo"
[1] "bar"
> print.and.return(verbose=FALSE)
[1] "bar"
> 

Answer 3

You may use hidden functional nature of R, for instance by defining function

deprintize<-function(f){
 return(function(...) {capture.output(w<-f(...));return(w);});
}

that will convert 'printing' functions to 'silent' ones:

noisyf<-function(x){
 print("BOO!");
 sin(x);
}

noisyf(7)
deprintize(noisyf)(7)
deprintize(noisyf)->silentf;silentf(7)

Answer 4

I agree with hadley and mbq's suggestion of capture.output as the most general solution. For the special case of functions that you write (i.e., ones where you control the content), use message rather than print. That way you can suppress the output with suppressMessages.

print.and.return2 <- function() {
  message("foo")
  return("bar")
}

# Compare:
print.and.return2()
suppressMessages(print.and.return2())