Reshape a numpy array

Question

Although I have tried np.reshape and transpose, I am not getting the desired output.

I have a numpy array that looks like this:

>>> a = np.array([[1, 1, 2, 2],[1, 1, 2, 2],[1, 1, 2,2]])
>>> a
array([[1, 1, 2, 2],
       [1, 1, 2, 2],
       [1, 1, 2, 2]])

I want the following:

>>> b = np.array([[1, 2],[1,2],[1,2],[1, 2],[1,2],[1,2]])
>>> b
array([[1, 2],
       [1, 2],
       [1, 2],
       [1, 2],
       [1, 2],
       [1, 2]])

The best I can do is in four lines of code:

e, f = np.hsplit(a,2)
e = e.reshape(np.size(e))
f = f.reshape(np.size(f))
b = np.vstack((e,f)).T

Can someone provide me with the pythonic way to reshape an array in this manner?

Would b = np.reshape(a,(6,2),'F') be enough?

Daniel
– Daniel

2016-01-27 21:47:05 +00:00
Commented Jan 27, 2016 at 21:47 — Daniel
– Daniel, Commented Jan 27, 2016 at 21:47

James McCormac · Accepted Answer · 2016-01-27 21:49:07Z

1

It is not clear exactly what you are looking for by only using 1s and 2s in the example. Please use letters or unique numbers so the mapping is clearer.

I was able to do some jiggling to make it work but I'm not 100% if this is the mapping you want. See the steps below:

>>> a = np.array([[1, 1, 2, 2],[1, 1, 2, 2],[1, 1, 2,2]])

array([[1, 1, 2, 2],
       [1, 1, 2, 2],
       [1, 1, 2, 2]])


>>> a.reshape(6,2)

array([[1, 1],
       [2, 2],
       [1, 1],
       [2, 2],
       [1, 1],
       [2, 2]])

>>> a.reshape(6,2).transpose()

array([[1, 2, 1, 2, 1, 2],
       [1, 2, 1, 2, 1, 2]])

>>> a.reshape(6,2).transpose().reshape(6,2)

array([[1, 2],
       [1, 2],
       [1, 2],
       [1, 2],
       [1, 2],
       [1, 2]])

answered Jan 27, 2016 at 21:49

James McCormac

1,7053 gold badges14 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Reshape a numpy array

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related