how to replace a character in an array using numpy?

Question

I have an array that consists of numeric values that are on a string form along with the '?' character which represents missing values. How can I make to replace those chars with an outlier value like -999999?

I know there is a way with Panda´s, but how to do that only using numpy? Tried to find those values with something like:

x=X[X=='?']

to use numpy replace, but no luck at all. Any help?

Thanks

jakevdp · Accepted Answer · 2018-09-08 05:04:53Z

4

It's quite similar to the Pandas method:

X[X == '?'] = '-999999'

at which point, if you desire, you could convert the values to integers using

X = X.astype(int)

For example:

import numpy as np
X = np.array(['1', '2', '3', '?', '5'], dtype=object)
X[X == '?'] = '-999999'
X = X.astype(int)
print(X)
# array([      1,       2,       3, -999999,       5])

edited Sep 8, 2018 at 5:04

answered Sep 8, 2018 at 4:26

jakevdp

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Sruthi · Accepted Answer · 2018-09-08 04:30:24Z

2

One way to do it would be using numpy.place :

np.place(X,X=="?",-999999)

answered Sep 8, 2018 at 4:30

Sruthi

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Cleb · Accepted Answer · 2018-09-09 20:57:48Z

0

You can also use np.where:

print(np.where(X == '?', '-999999', X).astype(int))

answered Sep 9, 2018 at 20:57

Cleb

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