How to hide or disable in-function printed message

Question

Suppose I have a function such as:

ff <- function(x) {
  cat(x, \"\\n\")
  x^2}

And run it by:

y <- ff(5)
# 5 
y
# [1         


        

Answer 1

You should also check out purrr::quietly().

ff <- function(x) {
  cat(x, "\n")
  x^2
}

purrr::quietly(ff)(7)$result
#> [1] 49

^{Created on 2020-09-10 by the reprex package (v0.3.0)}

Answer 2

You can use capture.output with invisible

> invisible(capture.output(y <- ff(2)))
> y
[1] 4

or sink

> sink("file")
> y <- ff(2)
> sink()
> y
[1] 4

Answer 3

Here's a nice function for suppressing output from cat() by Hadley Wickham:

quiet <- function(x) { 
  sink(tempfile()) 
  on.exit(sink()) 
  invisible(force(x)) 
} 

Use it like this:

y <- quiet(ff(5))

Source: http://r.789695.n4.nabble.com/Suppressing-output-e-g-from-cat-td859876.html