numpy array creating with a sequence

Question

I am on my transitional trip from MATLAB to scipy(+numpy)+matplotlib. I keep having issues when implementing some things. I want to create a simple vector array in three dif

Answer 1

Just want to point out for any other people going from MATLAB to Numpy that you can construct an np.r_ array with colons and then use it to index

E.g., if you have in matlab

arr_ones = ones(10,10)

Or in Numpy

arr_ones = np.ones([10,10])

You could in Matlab take only columns 1 through 5 as well as 7 like this:

arr_ones(:,[1:5 7])

Doing the same in Numpy is not (at least for me) intuitive. This will give you an "invalid syntax" error:

arr_ones[:,[1:5,7]]

However this works:

inds = np.r[1:5,]
arr_ones[:,inds]

I know this is not technically a new answer, but using a colon to construct an array when indexing into a matrix seems so natural in Matlab, I am betting a lot of people that come to this page will want to know this. (I came here instead of asking a new question.)