Jupyter Notebook rpy2 Rmagics: How to set the default plot size?

Question

I'm using the %%R cell magics in Jupyter notebooks. I'm aware that you can set the plot size for each cell with, e.g.:

%%R -w 800 -h 600

But I would like to set a default for the whole notebook/R session.

I've looked at the documentation, seen this blog post on the R Jupyter Notebook Kernel, and have seen Plot Size - Using ggplot2 in IPython Notebook (via rmagic) on setting the plot size by cell, but unless I've missed something obvious, there doesn't appear to be a way to set the default plot size for plots in R magics.

Is this possible? Is there a hidden setting, or must -w and -h be set for every cell individually?

Answer 1

Old question, but I just had the same itch, found this page, and then managed to scratch it, so hopefully this is useful to someone.

The workaround is monkey-patching rpy2 which calls R's png method directly without a way to set default arguments. Note that this approach is usually a Bad Idea, and brittle, but cannot be avoided. It would probably be worthwhile to make a feature request for rpy2 to include a mechanism for default arguments.

So here goes the monkey-patching:

# these are the defaults we want to set:
default_units = 'in' # inch, to make it more easily comparable to matpplotlib
default_res = 100 # dpi, same as default in matplotlib
default_width = 10
default_height = 9
# try monkey-patching a function in rpy2, so we effectively get these
# default settings for the width, height, and units arguments of the %R magic command
import rpy2
old_setup_graphics = rpy2.ipython.rmagic.RMagics.setup_graphics

def new_setup_graphics(self, args):
    if getattr(args, 'units') is not None:
        if args.units != default_units: # a different units argument was passed, do not apply defaults
            return old_setup_graphics(self, args)
    args.units = default_units
    if getattr(args, 'res') is None:
        args.res = default_res
    if getattr(args, 'width') is None:
        args.width = default_width
    if getattr(args, 'height') is None:
        args.height = default_height        
    return old_setup_graphics(self, args)

rpy2.ipython.rmagic.RMagics.setup_graphics = new_setup_graphics