How to count total times in numpy array where first column >1 and second column is <1

Question

I have numpy array like below I want to count total times columnsa>1 and columnsb<1

array

   [[1.2, 0.693],
   [1.2, 0.724],
   [0.976, 0.039],
   [0.987, 0.725],
   [0.979, 0.528],
   [0.978, 0.600],
   [0.983, 0.654],
   [0.986, 0.059],
   [0.979, 0.644],
   [0.982, 0.468]])]

Answer should yield 2

willeM_ Van Onsem · Accepted Answer · 2019-11-14 21:48:59Z

4

We can obtain the first column with arr[:,0] and the second with arr[:,1]. We can then make checks with arr[:,0] > 1 and arr[:,1] < 1. By using an AND operator (&), we obtain an array where an element is True if and only if the two corresponding elements are True. Finally we can sum up the booleans to obtain the number of times this is True:

>>> ((arr[:,0] > 1) & (arr[:,1] < 1)).sum()
2

answered Nov 14, 2019 at 21:48

willeM_ Van Onsem

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