Remove geom(s) from an existing ggplot chart?

Question

I am trying to understand how I can make changes to the internals of a ggplot2 chart. I started reading the few ressources I could find about ggplot_built and ggplot_gtable, but I could not answer the question below.

Given a plot g with 2 geom.

g <- ggplot(iris, aes(Petal.Length, Petal.Width)) +    geom_point() +    geom_text(aes(label=Sepal.Width)) g 

Is there a way to dive into the g object and remove one/multiple geoms?

Can I get, starting from g, a plot with no geoms?

Or with just the geom_text removed?

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UPDATE after more thorough testing of the answers

I just noticed that removing geoms can have an impact on the layout of the other geoms. Probably great as a default and the intended behaviour for most use cases, but I actually need the exact same chart "layout" (axis and positions of remaining geoms).

Example, before removing one geom:

library(dplyr) library(ggplot2) count(mpg, class) %>%   mutate(pct=n/sum(n)) %>%   ggplot(aes(class, pct)) +   geom_col(fill="blue") +   geom_line(group=1) +   geom_point(size=4)  

after removing one geom (note that the y axis doesn't start at 0 anymore, I guess the default behaviour for line/point without bars):

library(dplyr) library(ggplot2) count(mpg, class) %>%   mutate(pct=n/sum(n)) %>%   ggplot(aes(class, pct)) +   geom_col(fill="blue") +   geom_line(group=1) +   geom_point(size=4) -> p p$layers[[1]] <- NULL p 

Any ways to force ggplot to keep the exact same layout?

Answer 1

You can access / manipulate g's elements the way you would do with other R object.

g$layers #[[1]] #geom_point: na.rm = FALSE #stat_identity: na.rm = FALSE #position_identity   #[[2]] #mapping: label = Sepal.Width  #geom_text: parse = FALSE, check_overlap = FALSE, na.rm = FALSE #stat_identity: na.rm = FALSE #position_identity  

Remove geom_text:

g$layers[[2]] <- NULL 

Remove all layers

g$layers <- NULL g 

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The gginnards package offers some functions to manipulate ggplot layers, see the vignette User Guide: 4 Manipulation of plot layers for details.

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edit

Following the question of How can I extract plot axes' ranges for a ggplot2 object? I came to a solution that uses ggplot_build and ggplot_gtable. The idea is simply to copy the layout parameters taken from ggplot_built(p) to the new plot, for which we deleted a layer.

# create a copy of p p_new <- p  # delete the first layer p_new$layers[[1]] <- NULL p_new_build <- ggplot_build(p_new)  # this is the important line p_new_build$layout$panel_params <- ggplot_build(p)$layout$panel_params  library(gridExtra) grid.arrange(p, ggplot_gtable(p_new_build), ncol = 2)