Sahil
Sahil

Reputation: 439

How to reshape an array of shape (N , N) dimension to (N , N , 3)

I have an array of shape ( 2084, 2084) i want to reshape it to (2084, 2084 , 3). I tried using np.dstack but it gives me something like this (1, 2084, 2084)

patch = (2084, 2084)
patch_new = np.dstack(patch)

How do I do it?

Upvotes: 0

Views: 223

Answers (3)

kmario23
kmario23

Reputation: 61365

You missed promoting your array to 3D before depth stacking. So, you can use something like:

In [93]: patch = (2084, 2084)

In [94]: arr = np.random.random_sample(patch)

# make it as 3D array
In [95]: arr = arr[..., np.newaxis]

# and then stack it along the third dimension (say `n` times; here `3`)
In [96]: arr_3d = np.dstack([arr]*3)

In [97]: arr_3d.shape
Out[97]: (2084, 2084, 3)

Another way to do the same is (i.e. if you don't wish to promote your input array explicitly to 3D):

In [140]: arr_3d = np.dstack([arr]*3)
In [141]: arr_3d.shape
Out[141]: (2084, 2084, 3)

# sanity check
In [146]: arr_3 = np.dstack([arr[..., np.newaxis]]*3)

In [147]: arr_3.shape
Out[147]: (2084, 2084, 3)

In [148]: np.allclose(arr_3, arr_3d)
Out[148]: True

Upvotes: 1

hpaulj
hpaulj

Reputation: 231395

In [730]: x = np.arange(8).reshape(2,4)                                         
In [731]: x                                                                     
Out[731]: 
array([[0, 1, 2, 3],
       [4, 5, 6, 7]])

Your dstack not only adds an initial dimension, it transposes the rest. That's because it treats your array as a list, np.dstack([x[0,:], x[1,:]]).

In [732]: np.dstack(x)                                                          
Out[732]: 
array([[[0, 4],
        [1, 5],
        [2, 6],
        [3, 7]]])

This is a repeat task

In [733]: np.repeat(x[...,None],3,axis=2)                                       
Out[733]: 
array([[[0, 0, 0],
        [1, 1, 1],
        [2, 2, 2],
        [3, 3, 3]],

       [[4, 4, 4],
        [5, 5, 5],
        [6, 6, 6],
        [7, 7, 7]]])

Upvotes: 1

nibortolum
nibortolum

Reputation: 9

Kmario, so you repeat the same array 3 times over the third dimension ?

Upvotes: 0

Related Questions