Hi
Mostly these are bugs.
One source of confusion: wrap=FALSE is NOT doing better than wrap=TRUE,
which you can see if you start a new page before drawing the grabbed
grob ...
xyplot(1:5 ~ 1:5)
trellis.focus()
panel.abline(h = 3)
panel.abline(h = 5)
myGrob <- grid.grab(wrap = FALSE)
## start new page, otherwise just drawing over the top
grid.newpage()
grid.draw(myGrob)
But you are correct that wrap=TRUE is underperforming. The problem is
that your code is producing two grobs with the same name (and
grid.grab() gets upset because you cannot create a gTree with two grobs
with the same name).
Here is a workaround (make sure that each grob has a different name) ...
xyplot(1:5 ~ 1:5)
trellis.focus()
panel.abline(h = 3)
panel.abline(h = 5, identifier="abline2")
myGrob <- grid.grab()
grid.grab(wrap=TRUE) does not fix the problem because it does not wrap
grobs. For a more permanent solution, I have added a 'wrap.grobs'
argument to grid.grab() (in r-devel), so that you can now do this
(wrap.grobs=TRUE implicitly sets wrap=TRUE) ...
xyplot(1:5 ~ 1:5)
trellis.focus()
panel.abline(h = 3)
panel.abline(h = 5)
myGrob <- grid.grab(wrap.grobs = TRUE)
I have also fixed grid.grab() so that it does not complain about grobs
with the same name if you have set wrap.grobs=TRUE.
Thanks for the report. I hope this fixes the problems for you.
Paul
On 31/10/18 7:34 AM, John G. Bullock wrote:
grid.grab() captures all of the current viewports and stores them as a
grob. In theory, and often in practice, you can use grid.grab() to store
an image now for drawing later on. But I have noticed some odd behavior
of grid.grab() when working with lattice output. It is all related to
the wrap argument:
1. When wrap = TRUE, the saved grob should produce a drawing faithful to
the original viewports. But sometimes it doesn't.
2. wrap = FALSE is supposed to produce less faithful output if it
differs at all, but sometimes its output is more faithful.
3. Even when using wrap = TRUE, grid.grab() warns me to use wrap =
TRUE.
Here is a minimal example to illustrate all of these behaviors:
library(grid)
library(lattice)
xyplot(1:5 ~ 1:5)
trellis.focus()
panel.abline(h = 3)
panel.abline(h = 5)
myGrob <- grid.grab(wrap = TRUE)
At this point, I receive a warning --
In grabDL(warn, wrap, ...) :
one of more grobs overwritten (grab WILL not be faithful; try
'wrap = TRUE')
-- which is strange, given that I specified wrap = TRUE.
I proceed by running grid.draw(myGrob). According to Paul Murrell (R
Graphics, 2nd ed., page 239), using grid.grab(wrap = TRUE) is
"guaranteed to replicate the original output." But it doesn't.
Specifically, the top horizontal line (from panel.abline(h = 5)) isn't
reproduced.
Matters get stranger when I consider the following code:
xyplot(1:5 ~ 1:5)
trellis.focus()
panel.abline(h = 3)
panel.abline(h = 5)
myGrob <- grid.grab(wrap = FALSE)
grid.draw(myGrob)
These commands are the same as in the previous example, except that this
time, wrap = FALSE. But this time, grid.draw() does faithfully reproduce
the captured viewports. So the behavior is the opposite of what I
expect: when wrap = FALSE, grid.draw() faithfully reproduces the
captured viewports, but when wrap = TRUE, it doesn't.
I've run these examples in R 3.3.2 and 3.5.1. (Session info from 3.3.2
is appended.) The result is the same in both cases. Are these bugs, or
am I overlooking something?
Thank you,
John Bullock
> sessionInfo()
R version 3.3.2 (2016-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 17134)
locale:
[1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United
States.1252 LC_MONETARY=English_United States.1252 LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] grid stats graphics grDevices utils datasets methods base
other attached packages:
[1] lattice_0.20-34 RevoUtilsMath_10.0.0
loaded via a namespace (and not attached):
[1] RevoUtils_10.0.2
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--
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
p...@stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
