Last Updated on September 11, 2012 by nghiaho12

As part of my Python learning, Numpy in particular, I’ve ported rigid_transform_3D.m to Python. You can download it from at the bottom of the page.

My first impression of using Numpy to port the Matlab script hasn’t been too thrilling. The syntax isn’t as a nice to use as Matlab/Octave. The choice between using an array or matrix type have different trade offs. If I use an array (as recommended by the short answer) I can’t use the * to perform a standard matrix multiplication, a bit annoying to say the least. Indexing a matrix is slightly different compared to Matlab, for example A[0:3] means elements 0,1,2 but not 3 (not a big deal). Another problem I found was trying to do an outer product using dot(A, A.T) or dot(A.T, T), which returned a scalar value instead of a matrix. It seems arrays don’t make a distinction between row/column vector. The solution was to explicitly use the numpy.outer function.

Other than those small pet peeves (so far), I haven’t come across anything show stopping yet. I guess I have to tell myself that Python is a general purpose scripting language, unlike Matlab/Octave which was designed with matrices being the fundamental data type.