Numpy: Filtering rows by multiple conditions?
18,227
Solution 1
you can use multiple filters in a slice, something like this:
x = np.arange(90.).reshape(30, 3)
#set the first 10 rows of cols 1,2 to be zero
x[0:10, 0:2] = 0.0
x[(x[:,0] == 0.) & (x[:,1] == 0.) & (x[:,2] > 10)]
#should give only a few rows
array([[ 0., 0., 11.],
[ 0., 0., 14.],
[ 0., 0., 17.],
[ 0., 0., 20.],
[ 0., 0., 23.],
[ 0., 0., 26.],
[ 0., 0., 29.]])
Solution 2
How about this -
meta[meta[:,2]<X * np.all(meta[:,0:2]==0,1),:]
Sample run -
In [89]: meta
Out[89]:
array([[ 1, 2, 3, 4],
[ 0, 0, 2, 0],
[ 9, 0, 11, 12]])
In [90]: X
Out[90]: 4
In [91]: meta[meta[:,2]<X * np.all(meta[:,0:2]==0,1),:]
Out[91]: array([[0, 0, 2, 0]])
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Author by
sten
Updated on June 04, 2022Comments
-
sten almost 2 years
I have a two-dimensional numpy array called
meta
with 3 columns.. what I want to do is :- check if the first two columns are ZERO
- check if the third column is smaller than X
- Return only those rows that match the condition
I made it work, but the solution seem very contrived :
meta[ np.logical_and( np.all( meta[:,0:2] == [0,0],axis=1 ) , meta[:,2] < 20) ]
Could you think of cleaner way ? It seem hard to have multiple conditions at once ;(
thanks
Sorry first time I copied the wrong expression... corrected.
-
Joran Beasleythat doesnt work ... it will fail when both cases are false
-
Mazdakhow it works with
==
? you neednumpy.logical_and