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] 25 

My question is how to disable or hide the 5 printed from cat(x, "\n") such as:

y <- ff(5) y # [1] 25 

Answer 1

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 2

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