Make it easy to convert R variables to Sage

[kcrisman]

This was initially requested at this ask.sagemath.org question.

Question:

If I have a bunch of notebook cells with R code using the %r method, 
is there an easy way to grab the data as a varible in Python/Sage 
without converting the whole thing to use r.command syntax?

My answer, which I think should now be wrapped somehow given that it got three upvotes (a lot for ask.sagemath):

Victory! I knew this should be possible.
In the notebook:
%r
a <- c(1,2,3)
a

[1] 1 2 3

from sage.interfaces.r import RElement
b = RElement(r,'a')
c = b._sage_()
c

[1, 2, 3]
and then you can do stuff to c because it's not an RElement.
c[1] = 3
c

[1, 3, 3]
I don't know whether this is worth wrapping slightly better, 
or if that is even possible. But hopefully this works for you!

Note that this will only work for things with a nice conversion - but better than the current situation.

Component: packages: standard

Keywords: R, r-project

Issue created by migration from https://trac.sagemath.org/ticket/12010

[mwhansen]

comment:2

You can just do r('a')._sage_().

[kcrisman]

comment:3

Hmm, nice work; you always know how to make it easy!

So maybe this ticket should be about adding this type of example to the r? documentation, because I don't think there is much about using it in the notebook right now, but I bet a lot of people would like to know this.

Unless you can think of an even shorter or underscore-less syntax that would make sense for this...

[kcrisman]

Changed keywords from none to R, r-project