Inserting NaN in specific index(positions) in a numpy.array in Python

Question

I have two arrays P and J. I want to insert C1=nan in P according to positions in J. But I am getting an error. I present the expected output.

import numpy as np
from  numpy import nan

J=np.array([[1, 4, 5, 7]])
P=np.array([[1.35961580e+03, 1.35179719e+03, 1.30676673e+03, 1.17569069e+02,
        5.19255443e+00, 5.19255443e+00, 5.19255443e+00, 1.00000000e-09]])
C1=nan

P=np.insert(P,J,[C1],axis=1)
print("Pnew =",[P])

The error is

in <module>
    P=np.insert(P,J,[C1],axis=1)

  File "<__array_function__ internals>", line 5, in insert

  File "C:\Users\USER\anaconda3\lib\site-packages\numpy\lib\function_base.py", line 4626, in insert
    raise ValueError(

ValueError: index array argument obj to insert must be one-dimensional or scalar

The expected output is

array([[1.35961580e+03, nan, 1.35179719e+03, 1.30676673e+03, nan, nan, 1.17569069e+02,
        nan, 5.19255443e+00, 5.19255443e+00, 5.19255443e+00, 1.00000000e-09]])

coral · Accepted Answer · 2022-07-16 11:11:33Z

1

You can use for loop to reach each item in J.

import numpy as np
from numpy import nan

J = np.array([[1, 4, 5, 7]])
P = np.array([[
    1.35961580e+03, 1.35179719e+03, 1.30676673e+03, 1.17569069e+02,
    5.19255443e+00, 5.19255443e+00, 5.19255443e+00, 1.00000000e-09
]])
C1 = nan

for i in J[0]:
    P = np.insert(P, i, [C1], axis=1)
print("Pnew =", [P])

answered Jul 16, 2022 at 11:11

coral

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Comments

Mahdi F. · Accepted Answer · 2022-07-16 11:16:17Z

1

You need to pass J.ravel() and C1 as value not list.

np.insert(P,J.ravel(),C1,axis=1)

array([[1.35961580e+03,            nan, 1.35179719e+03, 1.30676673e+03,
        1.17569069e+02,            nan, 5.19255443e+00,            nan,
        5.19255443e+00, 5.19255443e+00,            nan, 1.00000000e-09]])

If you want to get the exactly desired output, you need to set (1,3,3,4) for J.

>>> np.insert(P,(1,3,3,4),C1,axis=1)
array([[1.35961580e+03,            nan, 1.35179719e+03, 1.30676673e+03,
                   nan,            nan, 1.17569069e+02,            nan,
        5.19255443e+00, 5.19255443e+00, 5.19255443e+00, 1.00000000e-09]])

edited Jul 16, 2022 at 11:16

answered Jul 16, 2022 at 11:09

Mahdi F.

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Comments

vignesh kanakavalli · Accepted Answer · 2022-07-16 11:08:51Z

0

import numpy as np

J = np.array([[1, 4, 5, 7]])
P = np.array([[1.35961580e+03, 1.35179719e+03, 1.30676673e+03, 1.17569069e+02,
               5.19255443e+00, 5.19255443e+00, 5.19255443e+00, 1.00000000e-09]])

P = np.insert(P, J.tolist()[0], [np.nan], axis=1)
print("Pnew =", P)

answered Jul 16, 2022 at 11:08

vignesh kanakavalli

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