Find Nth Smallest Element In Numpy Array

I need to find just the the smallest nth element in a 1D numpy.array. For example: a = np.array([90,10,30,40,80,70,20,50,60,0]) I want to get 5th smallest element, so my desired

Solution 1:

Unless I am missing something, what you want to do is:

>>> a = np.array([90,10,30,40,80,70,20,50,60,0])
>>> np.partition(a, 4)[4]
40

np.partition(a, k) will place the k-th smallest element of a at a[k], smaller values in a[:k] and larger values in a[k+1:]. The only thing to be aware of is that, because of the 0 indexing, the fifth element is at index 4.

Solution 2:

You can use heapq.nsmallest:

>>> import numpy as np
>>> import heapq
>>> 
>>> a = np.array([90,10,30,40,80,70,20,50,60,0])
>>> heapq.nsmallest(5, a)[-1]
40

Solution 3:

you don't need call numpy.max():

def nsmall(a, n):
    return np.partition(a, n)[n]