Create numpy array from matrix declared inside .m matlab file

Question

A coworker left some data files I want to analyze with Numpy.

Each file is a matlab file, say data.m, and have the following formatting (but with a lot more

Answer 1

Here are a couple options, although neither is built in.

The solution you probably do not find acceptable

This solution probably falls into your "quick and dirty" category, but it helps lead in to the next solution.

Remove the values = [, the last line (];), and globally replace all ; with nothing to get:

-24.92 -23.66 -22.55 
-24.77 -23.56 -22.45 
-24.54 -23.64 -22.56 

Then you can use numpy's loadtxt as follows.

>>> import numpy as np
>>> A = np.loadtxt('data.m')

>>> A
array([[-24.92, -23.66, -22.55],
       [-24.77, -23.56, -22.45],
       [-24.54, -23.64, -22.56]])

A solution you might find acceptable

In this solution, we create a method to coerce the input data into a form that numpy loadtxt likes (the same form as above, actually).

import StringIO
import numpy as np

def convert_m(fname):
    with open(fname, 'r') as fin:
        arrstr = fin.read()
    arrstr = arrstr.split('[', 1)[-1] # remove the content up to the first '['
    arrstr = arrstr.rsplit(']', 1)[0] # remove the content after ']'
    arrstr = arrstr.replace(';', '\n') # replace ';' with newline
    return StringIO.StringIO(arrstr)

Now that we have that, do the following.

>>> np.loadtxt(convert_m('data.m'))
array([[-24.92, -23.66, -22.55],
       [-24.77, -23.56, -22.45],
       [-24.54, -23.64, -22.56]])