python - 如果行的元素之一不满足条件，我如何删除数组的行？

Question

当数组第三列的元素小于特定数量时，我想删除数组的行。例如：

a=np.array([[2331.13,1944.88,23.1379,7,3.18339,0.482105],
[8168.44,1904.70,19.5025,265,4.12642,0.0376510],
[7389.36,1983.97,14.3581,3937,6.04109,0.713416],
[1765.18,1944.29,22.5495,35,2.30717,0.794432],
[2319.33,1946.68,22.4300,25,3.63676,0.0210690],
[785.666,2090.69,14.7940,1095,2.52823,0.999842],
[4071.24,2186.92,22.6616,31,2.79309,0.0312501],
[7082.51,2191.69,23.0122,19,2.53166,0.687001]])

我想删除满足以下条件的行：

a[:,2]<15.0

干杯。

Answer 1

你可以做：

a[a[:,2]>=15.0, :]

a[:,2]<15.0请注意to的反转a[:,2]>=15.0，以便您描述要保留而不是删除的行。

如果反转你的条件不是那么简单，你也可以使用~：

a[~(a[:,2]<15.0), :]

Answer 2

我认为删除行或列最直接的方法是使用np.delete

>>> a = np.arange(16).reshape(4,4)
>>> a
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])
>>> a[:,2]
array([ 2,  6, 10, 14])
>>> to_remove = a[:,2] < 7
>>> to_remove
array([ True,  True, False, False], dtype=bool)
>>> new_a = np.delete(a, to_remove, axis=0)
>>> new_a
array([[ 8,  9, 10, 11],
       [12, 13, 14, 15]])

在一行中：

new_a = np.delete(a, a[:,2] < 7, axis=0)