Mixing R, Python, and Perl in 14 Lines of Code

This is a continuation of my previous post, Running Python and R inside Emacs. That post shows how to execute independent code blocks in Emacs org-mode. This post illustrates calling one code block from another, each written in a different language.

The example below computes sin²(x) + cos²(x) by computing the sine function in R, the cosine function in Python, and summing their squares in Perl. As you’d hope, it returns 1. (Actually, it returns 0.99999999999985 on my machine.)

To execute the code, go to the #+call line and type C-c C-c.

#+name: sin_r(x=1)
#+begin_src R
sin(x)
#+end_src

#+name: cos_p(x=0)
#+begin_src python
import math
return math.cos(x)
#+end_src

#+name: sum_sq(a = 0, b = 0)
#+begin_src perl
$a*$a + $b*$b;
#+end_src

#+call: sum_sq(sin_r(1), cos_p(1))

Apparently each function argument has to have a default value. If that’s documented, I missed it. I gave the sine and cosine functions default values that would cause the call to sum_sq to return more than 1 if the defaults were used.


Source: http://www.johndcook.com/blog/2012/02/09/mixing-r-python-and-perl-in-13-lines-of-code/