Select two rows from bit array based on int array python

Question

I have two arrays one Int, and one is bit

s = [ [1]          x = [ [1 0 0 0 0]
      [4]              [1 1 1 1 0]
      [9]              [0 1 1 1 0]
      [0]              [0 0 1 0 0]
      [3] ]            [0 1 1 0 0]]

I want to find the smallest two elements in s (random given) then (select and print) two rows from x (random given) based on s array, for example, the smallest elements in s[i] are s[3]=0, s[0]=1, so i want to select x[3][0 0 1 0 0], and x[0][1 0 0 0 0]

import numpy as np
np.set_printoptions(threshold=np.nan)
s= np.random.randint(5, size=(5))
x= np.random.randint (2, size=(5, 5))
print (s)
print (x)

I tried my best using the "for loop" but no luck, any advice will be appreciated.

Please share your effort on your for-loop so that we can help you fix or correct it. — BusyProgrammer
– BusyProgrammer, Commented Feb 27, 2017 at 21:55
I love too, but it is not very clear otherwise I will share it, thanks — azeez
– azeez, Commented Feb 27, 2017 at 22:19

akuiper · Accepted Answer · 2017-02-27 21:48:00Z

1

You can use numpy.argpartition to find out the index of the two smallest elements from s and use it as row index to subset x:

s
# array([3, 0, 0, 1, 2])

x
# array([[1, 0, 0, 0, 1],
#        [1, 0, 1, 1, 1],
#        [0, 0, 1, 0, 0],
#        [1, 0, 0, 1, 1],
#        [0, 0, 1, 0, 1]])

x[s.argpartition(2)[:2], :]
# array([[1, 0, 1, 1, 1],
#        [0, 0, 1, 0, 0]])

answered Feb 27, 2017 at 21:48

akuiper

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1 Comment

azeez Over a year ago

Thank you so much that was very helpful

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