Using ggsave with a pipe

Question

I can save a plot with ggsave after I stored it, but using it in a pipeline I get the following error. I wish to plot and save in the same (piped) command.

  no applicable method for 'grid.draw' applied to an object of class "c('LayerInstance', 'Layer', 'ggproto', 'gg')" 

I know ggsave's arguments are first the filename, and then the plot, but switching this in a wrapper does not work. Also, using 'filename=' and 'plot=' in the ggsave command does not work.

library(magrittr)
library(ggplot2)
data("diamonds")

# my custom save function
customSave <- function(plot){
    ggsave('blaa.bmp', plot)
}

#This works:
p2 <- ggplot(diamonds, aes(x=cut)) + geom_bar()
p2 %>% customSave()

# This doesn't work:
ggplot(diamonds, aes(x=cut)) + geom_bar() %>% customSave()

# and obviously this doesn't work either
ggplot(diamonds, aes(x=cut)) + geom_bar() %>% ggsave('plot.bmp')

Answer 1

Update: The following code no longer works. See the tidyverse GitHub issue and another StackOverflow question for the official solution.

Original answer that NO LONGER WORKS:

If you want to plot and save in one line, try this

ggsave('plot.bmp') ```

If you don't want to show the plot, simply put `p <- ` at the
beginning. 

If you have a custom save function, you can also do this

``` mysave <- function(filename) {   ggsave(file.path("plots",
paste0(filename, ".png")), 
         width = 8, height = 6, dpi = 300) } ```

and simply replace `ggsave('plot.bmp')` with `mysave('plot')` in the
snippet above.

I found this usage by accident but haven't found any documentation.

Answer 2

As akrun pointed out, you need to wrap all of your ggplot in parentheses. You can also use the dot notation to pass an object to a function parameter other than the first in a magrittr pipe stream:

library(magrittr)
library(ggplot2)
data("diamonds")

(
  ggplot(diamonds, aes(x=cut)) +
    geom_bar()
) %>% 
  ggsave("plot.png", . , dpi = 100, width = 4, height = 4)