How to Install MatPlotLib for Ruby

MatPlotLib is a python library but it is pretty cool. I want to create plots using Rails so I need the bridge to ruby. Here is a rundown of what I did to get this work.

Install the Ruby-Python Bridge

Download and install ruby-python

I changed two macros in typemap.c from INT2FIX to INT2NUM because object pointers were being corrupted. I guess there is a slight performace hit.

/* store PyObject* as Integer in Hash */
#define PYOBJ2NUM(po) (INT2NUM((int)po))
#define NUM2PYOBJ(n) ((PyObject *)NUM2INT(n))

Also to compile with python2.4 I changed extconf.rb:

py_dir        = with_config("python-dir")
py_ver        = with_config("python-ver")

I added the second variable and did a global replace of python1.4 to #{py_ver}.

++++ Install MatPlotLib

I got debian packages for python-matplotlib from:

deb ./ # deb-src sources/

++++ Write some ruby code to generate a basic histogram

Following is python example

#!/usr/bin/env python from pylab import *

mu, sigma = 100, 15 x = mu + sigma*randn(10000)

# the histogram of the data n, bins, patches = hist(x, 50, normed=1) setp(patches, 'facecolor', 'g', 'alpha', 0.75)

# add a 'best fit' line y = normpdf( bins, mu, sigma) l = plot(bins, y, 'r--') setp(l, 'linewidth', 1)

xlabel('Smarts') ylabel('Probability') title(r'$\rm{Histogram\ of\ IQ:}\ \mu=100,\ \sigma=15$') axis([40, 160, 0, 0.03]) grid(True)

#savefig('histogram_demo',dpi=72) show()

Let's convert that into Ruby.

require 'python' require 'python/matplotlib' require 'python/matplotlib/backends' require 'python/matplotlib/cm'

include Py::MatPlotLib

mu, sigma = 100, 15 x = 1:1000.map{|m| sigma*rand()} + mu

# the histogram of the data n, bins, patches = hist(x, 50, normed=1) setp(patches, 'facecolor', 'g', 'alpha', 0.75) y = normpdf( bins, mu, sigma) l = plot(bins, y, 'r--') setp(l, 'linewidth', 1)

xlabel('Smarts') ylabel('Probability') title('\rm{Histogram\ of\ IQ:}\ \mu=100,\ \sigma=15') axis([40, 160, 0, 0.03]) grid(True)

show()