pytutorial/numpy/new_matrix

New matrices

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The goal

Making a new matrix...

Questions to David Rotermund

Using import numpy as np is the standard.

Simple example -- new np.zeros()

Define the size of your new matrix with a tuple, e.g.​

M = numpy.zeros((DIM_0, DIM_1, DIM_2, …))​

1d

import numpy as np

M = np.zeros((2))
print(M)

Output:

[0. 0.]

2d

import numpy as np

M = np.zeros((2, 3))
print(M)

Output:

[[0. 0. 0.]
 [0. 0. 0.]]

3d

import numpy as np

M = np.zeros((2, 3, 4))
print(M)

Output:

[[[0. 0. 0. 0.]
  [0. 0. 0. 0.]
  [0. 0. 0. 0.]]

 [[0. 0. 0. 0.]
  [0. 0. 0. 0.]
  [0. 0. 0. 0.]]]

Simple example -- recycle np.zeros_like()

If you have a matrix with the same size ​you want then you can use zeros_like. This will also copy other properties like the data type.

as a prototype use​

N = numpy.zeros_like(M) ​

import numpy as np

M = np.zeros((2, 3, 4))

N = np.zeros_like(M)
print(N)

Output:

[[[0. 0. 0. 0.]
  [0. 0. 0. 0.]
  [0. 0. 0. 0.]]

 [[0. 0. 0. 0.]
  [0. 0. 0. 0.]
  [0. 0. 0. 0.]]]

Remember unpacking

{: .topic-optional} This is an optional topic!

import numpy as np

d = (3, 4)
M = np.zeros((2, *d))

print(M)