Create ggplot2 plot in memory?

Question

I'm trying to capture the result of a ggplot2 graphic creation in memory, to send it to a server. Has anyone a good idea how to solve that?

My code looks currently like this:

data(mtcars)
x <- ggplot(mtcars, aes(x=mpg, y=hp)) +
  geom_point(shape=1)
print(x) # RStudio can capture the output, but I'm unable to do it.
ggsave(filename="a.jpg", plot=x) # not really a solution, need it not on disk, but as blob in memory.

What kind of a blob? Binary bitmap? ggplot list? To be consumed by what program? — Mike Wise
– Mike Wise, Commented Oct 2, 2015 at 11:56
@MikeWise The consumer is a program which accepts a python stringIO result - so it's just the content of a png read as "test" — Christian Sauer
– Christian Sauer, Commented Oct 2, 2015 at 12:09
I'm not sure if this will work, but maybe you can take advantage of SQLite's BLOB type - e.g. as in this blog post. — nrussell
– nrussell, Commented Oct 2, 2015 at 13:01
Would encoding the graphic into a base64 string be useful? The resulting character string could then be sent elsewhere. — Peter
– Peter, Commented Dec 15, 2017 at 19:36
Possible duplicate of In R, how to plot into a memory buffer instead of a file? — mlt
– mlt, Commented Dec 4, 2018 at 23:31

Bob · Accepted Answer · 2018-09-07 00:15:52Z

1

You can do this with the magick package.

library(magick)
data(mtcars)
x <- ggplot(mtcars, aes(x=mpg, y=hp)) +
  geom_point(shape=1)
fig <- image_graph(width = 400, height=400, res=96)
print(x)
dev.off()
figpng <- image_write(fig, path=NULL, format="png")

figpng is now a raw vector of a png of your plot.

answered Sep 7, 2018 at 0:15

Bob

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