How can I visualize the ggplot output from a function in an R script with rpy2?

Question

I am running R scripts inside a Python framework using the rpy2 package. I am running a function within an R script, which returns a ggplot as part of a larger collection. In Python, the class of this collection is either a rpy2.robjects.vectors.ListVector or an rpy2.rlike.container.OrdDict. (It is the former type in the toy example below).

Given this output of a ggplot in rpy2, how can I visualize the object? Other questions and examples I have seen deal with constructing the ggplot in rpy2; however, what I want to do is to work in rpy2 to visualize the ggplot that is output from an existing R script.

R script (ggtoy.R):

library(ggplot2)
data(Loblolly)

funfunfunction <- function(title="hello world!") {
  p <- ggplot(Loblolly, aes(x=height, y=age)) + geom_point()
  p <- p + ggtitle(title)
  
  l <- list("title"=title,"random"="something else")
  
  return(list("ggdict"=p,"sublist"=l))
  }

Python:

import rpy2.robjects as ro
from rpy2.robjects.lib import ggplot2

r_script_name = 'ggtoy.R' 
r_fn_name =  'funfunfunction'

params = { "title" : "new title!" }

ro.r(f"source('{r_script_name}', chdir = TRUE)") 
r_fn = ro.globalenv[r_fn_name]

r_fn_output = r_fn(**params)  

# stuck here
ggplot2.ggplot(r_fn_output[0])

I am unsure what to do with r_fn_output[0] to be able to engage with the ggplot image, either for visualization or download. It seems like there should be some easy way to do this in the high-level rpy2 API.

Asked By: stat_is_quo

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Source

Answer 1

At the very end of the rpy2.robjects.lib.ggplot2 script there is a convenient function ggplot2_conversion(), which is not documented elsewhere as far as I can find. Simply running this function on my ggplot/gg object worked great. It can then be visualized in iPython using rpy2.ipython.ggplot.image_png().

import rpy2.robjects as ro
from rpy2.robjects.lib import ggplot2
from rpy2.ipython.ggplot import image_png

r_script_name = 'ggtoy.R' 
r_fn_name =  'funfunfunction'

params = { "title" : "new title!" }

ro.r(f"source('{r_script_name}', chdir = TRUE)") 
r_fn = ro.globalenv[r_fn_name]

r_fn_output = r_fn(**params)  
converted = ggplot2.ggplot2_conversion(r_fn_output[0])
image_png(converted)

Answered By: stat_is_quo

How can I visualize the ggplot output from a function in an R script with rpy2?

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