Hi
baptiste auguie wrote:
Dear all,
I'm trying to access and modify grobs in a ggplot2 plot. The basic idea
for raw Grid objects I understand from Paul Murrell's R graphics book,
or this page of examples,
http://www.stat.auckland.ac.nz/~paul/grid/copygrob/copygrobs.R
However I can't figure out how to apply this to a ggplot (basically I
don't know how to write a syntactically correct gPath),
p <- # minimal example
qplot(0,0)+ annotate("text",0,0,label="test")
g <- # store the plot as a grob
ggplotGrob(p)
# structure of the grob
grid.ls(g) # rather large!
# find a particular grob in the gTree
getGrob(g,"texts", grep = T)
# next step, modify, say, the colour of these grobs
grid.edit() # what do I put in here?
(Ignoring whether this is the most ggplot-ish way to achieve the end
result ...)
Let's take a closer look at the part of the grob (gTree) that you have
selected ...
> grid.ls(getGrob(g,"texts", grep = T))
texts.gTree.5
GRID.text.3
... (the "5" and the "3" in those names are likely to be different for
you). This is a gTree with one child, which is a text grob. I don't
know much about how the "texts" gTree works, so it's not clear how I
should modify that to influence the text grob, but I do know that I can
modify the 'gp' component of the text grob. For example ...
> grid.edit("GRID.text.3", gp=gpar(col="red"))
... and if I wanted to be SURE that I was getting the text grob beneath
that "texts" gTree, then I could use a gPath like this ...
> grid.edit(gPath("texts.gTree.5", "GRID.text.3"), gp=gpar(col="blue"))
... and if I wanted to use code that had a better chance of working in
another session (when the "5" and "3" name suffixes are likely to be
different), I could use something like ...
> grid.edit(gPath("texts.gTree", "GRID.text"), grep=TRUE,
gp=gpar(col="pink"))
... does that give you what you were looking for ?
Paul
Thanks for any piece of advice,
baptiste
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The University of Auckland
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and provide commented, minimal, self-contained, reproducible code.
