Dear all,
Is there a possibility to remove a geom from a ggplot? Background suppose I
have a function which returns a ggplot object after some data re-formatting and
aggregation. While this ggplot object is fine in 90% of the cases it turns out
that for some cases I want to suppress one of the layers which was added to the
plot.
I could look at the source code of the function and write a new one, which has
an additional flag parameter, with which I could ask the function to add or not
to add the geom, but this sounds a bit of overkill to me and it would be nice,
if I could just remove the particular layer?
An example is in order to make my point clearer:
library(ggplot2)
d <- data.frame(x=rep(1:10, each = 10), y = rnorm(100), grp = rep(1:10, 10))
makePlot <- function() {
ggplot(d, aes(x = x, y = y)) + stat_summary(fun.data = "mean_cl_normal",
color = "red") + geom_point()
}
(p <- makePlot())
## Now I want to have lines instead of points, but of course the points are
still there
p + geom_line(aes(group = grp, color = grp))
Again, it would not be difficult to rewrite makePlot to deal with that, but for
me this seems to be error prone / duplication. So ideally, I would like to do
something like:
p %-% geom_point()
which is ambiguous of course, as there can be several point layers in the plot.
Looking at
str(p)
I see that there is a layers slot, so I can do
q <- p
q$layers <- q$layers[-2]
q + geom_line(aes(group = grp, color = grp))
which does actually what I want.
However, is there a way to do that in a more automated way? For now I have to
inspect the object and to decide which layer I want to delete, otherwise I can
get something like this:
makePlot2 <- function() {
ggplot(d, aes(x = x, y = y)) + geom_point() + stat_summary(fun.data =
"mean_cl_normal", color = "red")
}
q <- makePlot2()
q$layers <- q$layers[-2]
q + geom_line(aes(group = grp, color = grp))
which removes the error bars but not the points (as the order in layers
changed). So any ideas how to proceed in this case? If there is a nice way, I
could even think of overloading %-% which would fit nicely in the idea of a
plot which can not only be added layer by layer, but where I also could remove
certain layers.
Maybe (and even probable) there is a very good idea why I should not do that at
all and I would be curious to hear these things as well. For now I am yet
interested to know how I can remove layers of a plot conveniently.
Thanks for your help!
Kind Regards,
Thorn Thaler
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