why unable to concatenate two arrays in python?

Question

I have two arrays

>>> array1.shape
(97, 195)
>>> array2.shape
(195,)
>>> array1 = numpy.concatenate((array1, array2), axis=0)

when I perform concatenate operation it shows an error

ValueError: all the input arrays must have same number of dimensions

is that the second array shape (195,) creating problem?

Transpose second array. From docs.scipy: The arrays must have the same shape, except in the dimension corresponding to axis (the first, by default). It should be (1,195). Than you can concatenate over 2nd dimension, obv — soupault
– soupault, Commented Jul 16, 2014 at 11:32
That's not a transpose, but you do want to reshape the array to (1, 195). — user2357112
– user2357112, Commented Jul 16, 2014 at 11:34
@s0upa1t: It's not a row vector or a column vector; it's 1-dimensional. Ask NumPy to transpose it (with transpose or T), and you'll find no change. — user2357112
– user2357112, Commented Jul 16, 2014 at 20:24

deinonychusaur · Accepted Answer · 2014-07-16 11:34:49Z

3

Just make both have the same dimensions and the same size except along the axis to be concatenated:

np.concatenate((array1, array2[np.newaxis,...]), axis=0)

answered Jul 16, 2014 at 11:34

deinonychusaur

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Comments

mmdanziger · Accepted Answer · 2014-07-16 11:35:35Z

1

In order for this to work, you need array2 to actually be 2d.

array1 = numpy.concatenate((array1, array2.reshape((1,195)))

should work

answered Jul 16, 2014 at 11:35

mmdanziger

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rroowwllaanndd · Accepted Answer · 2014-07-22 13:08:46Z

0

Another easy way to achieve the array concatenation that you’re looking for is to use Numpy’s vstack function as follows:

array1 = np.vstack([array1, array2])

answered Jul 16, 2014 at 13:39

rroowwllaanndd

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