给定值数组，我希望 Select 满足条件的多个连续元素序列.结果应该是每个元素序列对应一个array.
For example I have an array containing both negative and positive numbers. I need to select sequences of negative numbers, with each sequence in a separate array.
Here is an example :
import numpy as np
# Example data
values = np.array([1, 2, 3, -1, -2, -3, 4, 5, 6, -7, -8, 10])
mask = values < 0
下面是输出应该是什么样子:
Array 1:
[-1 -2 -3]
Array 2:
[-7 -8]
我试着用numpy.split来做这件事，但它变得更像意大利面代码.我想知道有没有一种毕达德式的方法来完成这项任务？
如果您只想对负值的块进行分组，而不考虑它们的相对值，那么只需计算第二个掩码来标识每个负值块的开始:
mask = values < 0
mask2 = np.r_[True, np.diff(mask)]
out = np.array_split(values[mask], np.nonzero(mask2[mask])[0][1:])
输出:[array([-1, -7, -3]), array([-7, -8])]
If you want to cluster the negative values that also a successively decreasing (e.g. -1, -2, -3, -5, -6 would form 2 clusters: -1, -2, -3 and -5, -6. Then I would use pandas:
Series(~mask).cumsum())groupby个import pandas as pd
s = pd.Series(values)
# mask to keep negative values
mask = s<0
# group consecutive negatives
group1 = (~mask).cumsum()
# group successive decrementing values
s2 = s+s.index
group2 = s2.ne(s2.shift()).cumsum()
out = [g.to_numpy() for k, g in s[mask].groupby([group1, group2])]
输出:[array([-1, -2, -3]), array([-7, -8]), array([-7])]
中间体:
s mask s2 group1 group2
0 1 False 1 1 1
1 2 False 3 2 2
2 3 False 5 3 3
3 -1 True 2 3 4 # out 1
4 -2 True 2 3 4 #
5 -3 True 2 3 4 #
6 4 False 10 4 5
7 5 False 12 5 6
8 6 False 14 6 7
9 -7 True 2 6 8 # out 2
10 -8 True 2 6 8 #
11 -7 True 4 6 9 # out 3
12 10 False 22 7 10