How to suppress qplot's binwidth warning inside a function? - r

Question

I am writing a function that uses qplot() to draw a histogram, for example,
> library(ggplot2)
> d=rnorm(100)
> myfun=function(x) qplot(x)
Running it gives a warning:
> myfun(d)
stat_bin: binwidth defaulted to range/30. Use 'binwidth = x' to adjust this.
To suppress the warning, I tried computing the binwidth myself, but this gives an error and doesn't plot:
> myfun=function(x) print(qplot(x, binwidth=diff(range(x))/30))
> myfun(d)
Error in diff(range(x)) : object 'x' not found
I have two related questions:
What is going on here? Why is object 'x' not found?
How can I write the function so the warning is not generated?
Thanks!

Answer 1

To attempt to clear up some confusion, this construct does not prevent the binwidth warnings/messages to appear:
suppressMessages(p <- ggplot(...))
print(p)
But this does:
p <- ggplot(...)
suppressMessages(print(p))
As Hadley's comment points out, lazy evaluation prevents the stat_* functions from actually running until they need to at print-time.

Answer 2

I can't explain the why of this one (Hadley may swing by and do so) but using ggplot instead of qplot solves the problem:
d <- data.frame(v1 = rnorm(100))
myfun <- function(x){
p <- ggplot(data = x, aes(x = v1)) +
geom_histogram(binwidth = diff(range(x$v1))/30)
print(p)
}
Doing it this way I get no warning message. Also, using ggplot and removing the binwidth = ... portion in geom_histogram makes the warning reappear, but then suppressMessages works as expected as well.
I suspect this has to do with namespaces or environments and when/where qplot and ggplot are evaluating arguments. But again, that's just a guess...

Answer 3

As they say on TV "Had this been a real warning you would have been given directions from your local authorities."
Since it wasn't a warning then my original answer didn't cause it to error out. This is what I should have written:
options(warnings= -1)
<do something> # no warnings
options(warnngs=1)
<business as usual>
But it wasn't a warning but a message to the console. Here's how to stop it:
con=file("temp.fil", "w")
sink(con, type="message")
library(ggplot2)
d=rnorm(100)
myfun=function(x) qplot(x)
myfun(d)
sink( type="message")