[R] How to suppress plotting for "xyplot(zoo(x))"?

[Gabor Grothendieck]

On Tue, Dec 21, 2010 at 8:40 AM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> On Tue, Dec 21, 2010 at 7:53 AM, Marius Hofert <m_hofert at web.de> wrote:
>> Hi,
>>
>> I found the thread http://r.789695.n4.nabble.com/Matrix-as-input-to-xyplot-lattice-proper-extended-formula-syntax-td896948.html
>> I used Gabor's approach and then tried to assign the plot to a variable (see below). But a Quartz device is opened... why? I don't want to have anything plot/printed, I just would like to store the plot object. Is there something like "plot = FALSE"?
>>
>> Cheers,
>>
>> Marius
>>
>> library(lattice)
>> library(zoo)
>>
>> df <- data.frame(y = matrix(rnorm(24), nrow = 6), x = 1:6)
>> xyplot(zoo(df[1:4], df$x), type = "p")
>>
>> plot.object <- xyplot(zoo(df[1:4], df$x), type = "p") # problem: a Quartz device is opened (on Mac OS X 10.6)
>
> This also opens up a window on Windows.   It occurs within lattice
> when lattice issues a trellis.par.get .  A workaround would be to open
> a device directed to null.  On Windows this would work.  I assume if
> you use "/dev/null" it would work on your machine.
>
> png("NUL")
> plot.object <- ...
> dev.off()

Also Yihui Xie found an undocumented NULL device which you could try  See:
  http://yihui.name/en/2010/12/a-special-graphics-device-in-r-the-null-device/

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