The function I'm asking for is just for convenience during programming. Adding layers in ggplot2 with the "+" operator is great. Especially adding layers in the middle amounts to just adding another line of code. However, if I want to try to add a layer after the last line, I have to append a "+" to the last row and if I want to remove this layer again, I also have to remove the "+" again:
ggplot(df, aes(x,y,...)) +
geom_X(...) + # after this line, I can easily add layers
... +
layer_Z(...) # to add a layer after here, I have to modify also this line
I'm searching for a function ggidentity() which just returns the plot itself to use it as a default last line so I can easily add more lines, as in
ggplot(df, aes(x,y,...)) +
geom_X(...) + # after this line, I can easily add layers
... +
layer_Z(...) + # now it's easy to add layers after this line
ggidentity() # this doesn't change anything in the plot
I tried it with a simple function
identity <- function(x) x
which works well with the magrittr-package (and improves my workflow in exploratory data analysis), but not with ggplot2.
I think we need geom_blank(), example:
library(ggplot2) # ggplot2_2.2.1
ggplot(mtcars, aes(wt, mpg)) +
geom_point() +
geom_blank() # The blank geom draws nothing