CODEWITHSUNDEEP
pythonarraysnumpyscipynumerical
Mark
Mark

Reputation: 1343

numpy unique strange behaviour

according to the official numpy.unique documentation (http://docs.scipy.org/doc/numpy/reference/generated/numpy.unique.html) return_index=True should allow me to recover the first occurrences of elements in an array. However, this does not work for this simple example:

import numpy as np
a = np.array([10,20,30,40,50,60,70,80,3,2,4,3,2,5,2,1,999,1000])
a = np.append(a,np.repeat(999,10000))
u, indices = np.unique(a, return_index=True)
print indices[13], u[13] #according to unique documentation indices[13] should be 16 (i.e. first occurrence of 999 = u[13]), but it is not

This results in:

[mvogelsberger@itc021 ~]$ python test.py 
6685 999

Clearly, 6685 is not the index of first occurrence of 999 in the array a. Can someone clarify? I probably misunderstand the documentation...

Thanks! Mark

Upvotes: 1

Views: 734

Answers (1)

ali_m
ali_m

Reputation: 74182

As you've guessed in the comments, this behaviour is indeed a bug that was fixed in Numpy v1.7

Upvotes: 2

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