inserting numpy data into a bigger array of zeros

Question

I would like to put data of a numpy array of any size from the start of another bigger array of zeros.

Looking at numpy documentation I found the function np.put but it gives me a problem like this:

Supossing

import numpy as np
b = np.zeros(5)
a = np.range(1,4)
np.put(b,a,a)

produces something in b like

[0,1,2,3,0]

I also tried to use place function

np.place(b,b>len(a),a)

but nothing changes the matrix.

[0,0,0,0,0]

If someone has already worked on this, his/her help would be really good now.

It's a bit difficult to understand the question, what is the behaviour you expect, and which command fails to do that? — Conor
– Conor, Commented Jun 8, 2016 at 16:34

piRSquared · Accepted Answer · 2016-06-08 16:40:30Z

1

You're using np.put incorrectly.

np.put(b, a, a)
#      ^  ^  ^
#      |  |  |
# Target  |  |
#   Indices  |
#       Values

You told np.put to place the values of a at positions defined by a.

Instead:

np.put(b, np.arange(len(a)), a)

or:

b[:len(a)] = a

answered Jun 8, 2016 at 16:40

piRSquared

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