Suppress output of a function

Question

I'm looking to suppress the output of one command (in this case, the apply function).

Is it possible to do this without using sink()? I've found the described solution below, but would like to do this in one line if possible.

How to suppress output

Stagestruck

Can you explain what you mean by 'do this inline'? Otherwise the question you cite already provides the answer and this is a duplicate. – Dote

This solution requires three lines, one redirecting output, the command, and then another to turn output back on. – Stagestruck

Or use capture.output. Or use *_ply from the plyr package. – Watts

I second Hadley's suggestion- if you are really trying to execute an apply function, such as lapply, without printing output then 'l_ply` from his plyr package is probably the most appropriate choice. – Nawab

Answer 1

It isn't clear why you want to do this without sink, but you can wrap any commands in the invisible() function and it will suppress the output. For instance:

1:10 # prints output
invisible(1:10) # hides it

Otherwise, you can always combine things into one line with a semicolon and parentheses:

{ sink("/dev/null"); ....; sink(); }

Koan

Try 'invisible(cat("Hi\n"))' -- invisible() only suppresses the print of an expression, it is not a sink() one-liner. – Dote

Right, but I think that it meets the needs of the questioner, unless I'm missing something in the question... – Koan

For instance, this suppresses the return of apply, as per the question: invisible(apply(matrix(1:10), 1, as.numeric)). – Koan

Rather than { sink("/dev/null"); ....; sink(); } I would definitely prefer capture.output, as capture.output effectively does exactly above, just a lot better (have a look at the source, it calls sink as in above fashion, plus some nice stuff around it). – Bartlett

doesn't work on idw function under Windows. I think the best solution is using sink – Yongyoni

Answer 2

Use the capture.output() function. It works very much like a one-off sink() and unlike invisible(), it can suppress more than just print messages. Set the file argument to "/dev/null" on UNIX or "NUL" on windows, or, better, use nullfile() (>= 3.6.0) for platform independence. If you need to support R< 3.6, use R.utils::nullfile(). For example, considering Dirk's note:

> invisible(cat("Hi\n"))
Hi

> capture.output(cat("Hi\n"), file = nullfile())
> 

Nawab

doesn't work if you want to apply this to a function which returns some value and you want to use this value – Yongyoni

@TMS Did something change during the last few month? I just tested to use the value returned by a function and it worked... capture.output(x <- log(2)) and afterwards x has the value of log(2)... – Industrialist

This did not work for output in red. – Jelsma

using nullfile() in your code is probably cleaner than platform-specific nullfile()/NUL ? – Gravely

Works alright! Actually for a ggplot I also combined afterwards a suppressMessages to hide it completely – Prudenceprudent

Answer 3

The following function should do what you want exactly:

hush=function(code){
  sink("NUL") # use /dev/null in UNIX
  tmp = code
  sink()
  return(tmp)
}

For example with the function here:

foo=function(){
  print("BAR!")
  return(42)
}

running

x = hush(foo())

Will assign 42 to x but will not print "BAR!" to STDOUT

Note than in a UNIX OS you will need to replace "NUL" with "/dev/null"

Leoraleos

This was the only answer that did what I needed, underrated. – Freefloating

exactly what i needed too – Deroo

This did not work for me, still getting red letters output – Jelsma

@SkyScraper - Can you please give a short toy example of what you're doing that causes this to fail? – Leoraleos

@Leoraleos I figured out the issue, the output was messages() and this approach does not function for this kind of output. I had to use suppressMessages() – Jelsma

Answer 4

R only automatically prints the output of unassigned expressions, so just assign the result of the apply to a variable, and it won't get printed.

Haematogenous

Some functions have a print() or cat() in them that goes to the screen, not to an assignment. – Dillard

Answer 5

you can use 'capture.output' like below. This allows you to use the data later:

log <- capture.output({
  test <- CensReg.SMN(cc=cc,x=x,y=y, nu=NULL, type="Normal")
})

test$betas

Abrade

This did not work for output in red. – Jelsma

Answer 6

In case anyone's arriving here looking for a solution applicable to RMarkdown, this will suppress all output:

```{r error=FALSE, warning=FALSE, message=FALSE}
invisible({capture.output({

# Your code goes here
2 * 2
# etc
# etc


})})
```

The code will run, but the output will not be printed to the HTML document

Reportage

Answer 7

Making Hadley's comment to an answer: Use of apply family without printing is possible with use of the plyr package

x <- 1:2
lapply(x, function(x) x + 1)
#> [[1]]
#> [1] 2
#> 
#> [[2]]
#> [1] 3

plyr::l_ply(x, function(x) x + 1)

Sarsenet

Answer 8

invisible(cat("Dataset: ", dataset, fill = TRUE))
invisible(cat(" Width: " ,width, fill = TRUE))
invisible(cat(" Bin1:  " ,bin1interval, fill = TRUE))
invisible(cat(" Bin2:  " ,bin2interval, fill = TRUE))
invisible(cat(" Bin3:  " ,bin3interval, fill = TRUE))

produces output without NULL at the end of the line or on the next line

Dataset:  17 19 26 29 31 32 34 45 47 51 52 59 60 62 63
Width:  15.33333

Bin1:   17 32.33333
Bin2:   32.33333 47.66667
Bin3:   47.66667 63

Fatigued

Answer 9

Here is a version that is robust to errors in the code to be shushed:

quietly <- function(x) {
  sink("/dev/null") # on Windows (?) instead use `sink("NUL")`
  tryCatch(suppressMessages(x), finally = sink())
}

• This is based directly on the accepted answer, for which thanks.
• But it avoids leaving output silenced if an error occurs in the quieted code.

Hermineherminia

OP asked for an answer which leaves out sink. – Loose

OP accepted an answer which works via sink. This answer updates the accepted answer to avoid a pitfall arising if an error occurs in the code the answer is applied to. – Hermineherminia

If your answer enhances an existing accepted answer its better practice to suggest an edit to that answer or suggest it as a comment below the answer. Regardless of what OP accepts, the answers provided should answer the question which is asked. Stack Overflow is a community. If someone else has the same question, wanting to avoid sink it will be marked as duplicate even though this question does not have an answer here. – Loose

Answer 10

If you're wondering how to suppress a warning() you can use suppressWarnings() like so:

suppressWarnings(warning("hi"))

Whereas these two will still show the warning:

invisible(warning("Hi"))
# shows 'Hi'

capture.output(warning("Hi"), file='NUL')
# shows 'Hi'

Reportage

Answer 11

for the return(something) part inside an R function:

return(invisible(something))  

works ok

invisible(return(something))

does not work at all

Otranto