Can the print() command in R be quieted?
In R some functions can print information and return values, can the print be silenced?
For example:
开发者_StackOverflow社区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"
?
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)
?capture.output
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"
>
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())
I know that I might be resurrecting this post but someone else might find it as I did. I was interested in the same behaviour in one of my functions and I just came across "invisibility":
It has the same use of return()
but it just don't print the value returned:
invisible(variable)
Thus, for the example given by @ayman:
print.and.return2 <- function() {
message("foo")
invisible("bar")
}
精彩评论