Adding dimension to ndarray and reshaping

Question

I have a numpy array that has shape of (16,2)

[[-109.12722222    1454.        ]
 [-109.12694444    1459.        ]
 [-109.12666667    1463.        ]
 [-109.12638889    1465.        ]
 [-109.12611111    1464.        ]
 [-109.12583333    1464.        ]
 [-109.12555556    1464.        ]
 [-109.12527778    1464.        ]
 [-109.125         1464.        ]
 [-109.12472222    1465.        ]
 [-109.12444444    1465.        ]
 [-109.12416667    1463.        ]
 [-109.12388889    1462.        ]
 [-109.12361111    1461.        ]
 [-109.12333333    1459.        ]
 [-109.12305556    1454.        ]]

and I want to know how to reshape it so it is (4,4,2).

[[-109.12722222    1454.        ] [-109.12694444    1459.        ][-109.12666667    1463.        ][-109.12638889    1465.        ]
 [-109.12611111    1464.        ] [-109.12583333    1464.        ] [-109.12555556    1464.        ][-109.12527778    1464.        ]
 [-109.125         1464.        ][-109.12472222    1465.        ][-109.12444444    1465.        ][-109.12416667    1463.        ]
 [-109.12388889    1462.        ][-109.12361111    1461.        ][-109.12333333    1459.        ][-109.12305556    1454.        ]]

I tried this:

numpy_array = np.reshape(4, 4, 2)

but it throws:

ValueError: cannot reshape array of size 1 into shape (4,)

how can you convert 2 dimensional array to three dimensional? — Kishan Mehta
– Kishan Mehta, Commented Aug 23, 2019 at 5:49
@Kishan there were people who did it here, but when I did that it still threw the same error stackoverflow.com/questions/7372316/… — raceee
– raceee, Commented Aug 23, 2019 at 5:55
Did you read the documentation on how to use numpy.reshape - docs.scipy.org/doc/numpy/reference/generated/numpy.reshape.html? — Divakar
– Divakar, Commented Aug 23, 2019 at 6:02

Abercrombie · Accepted Answer · 2019-08-23 05:58:17Z

3

You can make use of numpy.newaxis

import numpy as np

a = np.zeros((16, 2))
b = a[:, :, np.newaxis]
c = b.reshape(4, 4, 2)

print(c.shape)

answered Aug 23, 2019 at 5:58

Abercrombie

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2 Comments

raceee Over a year ago

Got it! I realized what I was forgetting, thanks for the answer.

hpaulj Over a year ago

a.reshape(4,4,2) or np.reshape(a, (4,4,2)) would work just as well. You don't need the newaxis step.

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