[R] Fwd: unexpected behavior of trellis calls inside a user-defined function

[Deepayan Sarkar]

Forgot to CC.

---------- Forwarded message ----------
From: Deepayan Sarkar <deepayan.sarkar at gmail.com>
Date: Mar 22, 2007 3:19 PM
Subject: Re: [R] unexpected behavior of trellis calls inside a
user-defined function
To: Jenny Bryan <jenny at stat.ubc.ca>


Hi,

I see lots of calls to trellis.focus(), but none to trellis.unfocus().
trellis.focus() sets the ``viewport'' to a particular panel. Unless
you go back to the root viewport, you will get stuck in a weird place
in the viewport tree. This is not a problem if your next plot is on a
new page, but will be otherwise.

So short anwser: call trellis.unfocus() when you are done doing
whatever you need to do after a trellis.focus() call.

Deepayan

On 3/22/07, Jenny Bryan <jenny at stat.ubc.ca> wrote:
> I am making a battery of levelplots and wireframes for several fitted
> models.  I wrote a function that takes the fitted model object as the
> sole argument and produces these plots.  Various strange behavior
> ensued, but I have identified one very concrete issue (illustrated
> below): when my figure-drawing function includes the addition of
> points/lines to trellis plots, some of the information (main title,
> placement of additional points) from my i-th function call is leaking
> over into the i+1-th call.  In the example below, I just get
> unexpected results.  In my actual application, it breaks the whole
> function and one of the error messages I've gotten is:
>
>  > figFun(smoothFit1) ## no longer worked, once I got fancy with trellis
> Error in depth(path) : no applicable method for "depth"
>
> Smallest example I could construct to illustrate at least one of my
> problems:
>
> predVals <-
>    expand.grid(list(Sepal.Length = seq(from = min(iris$Sepal.Length),
>                       to = max(iris$Sepal.Length), length = 50),
>                     Petal.Length = seq(from =  min(iris$Petal.Length),
>                       to = max(iris$Petal.Length), length = 50)))
> irisFit <- lm(Sepal.Width ~ Sepal.Length * Petal.Length, data = iris)
> predSurf <- data.frame(predVals, Sepal.Width = predict(irisFit,
> predVals))
> trellis.device("X11",width = 8, height = 8)
>
> levelplot(Sepal.Width ~ Sepal.Length * Petal.Length,
>            predSurf, main = "Produced at command line, Take 1")
>
> # put levelplot call inside a function
> myFunction <- function(surf) {
>    levelplot(Sepal.Width ~ Sepal.Length * Petal.Length,surf,
>              main = "Produced by function, Take 1")
> }
> myFunction(predSurf)
> # OK, get the expected figure result
>
> ## now .. what if we add points to the plot?
> levelplot(Sepal.Width ~ Sepal.Length * Petal.Length,
>            predSurf, main = "Produced at command line, Take 2")
> trellis.focus("panel", 1, 1)     # address the correct part of the
> figure
> lpoints(6,4,pch = 19, cex = 2)   # a point appears in correct location
> # I get what I expect
>
> ## any crosstalk from adjacent command line invocations?  no
> levelplot(Sepal.Width ~ Sepal.Length * Petal.Length,
>            predSurf, main = "Produced at command line, Take 3")
> trellis.focus("panel", 1, 1)     # address the correct part of the
> figure
> lpoints(5,2,pch = 19, cex = 2)   # a point appears in correct location
> # I get what I expect
>
> # put all this inside a function
> myFunction <- function(surf) {
>    levelplot(Sepal.Width ~ Sepal.Length * Petal.Length,surf,
> main = "Produced by function, Take 2")
> trellis.focus("panel", 1, 1)     # address the correct part of the
> lpoints(7,5,pch = 19, cex = 2)   # a point appears in correct location
> }
> myFunction(predSurf)
> # the title still says "Produced at command line, Take 3"
> # and points appear at (5,2) AND (7,5) ... why?
>
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