更新时间:2022-12-10 20:49:14
这是一个基于 numpy 的解决方案.
Here's a numpy-based solution.
我认为 (?) 它应该比其他选项更快.希望它相当清楚.
I think (?) it should be faster than the other options. Hopefully it's fairly clear.
然而,它需要的内存是各种基于生成器的解决方案的两倍.只要您可以在内存中保存数据的单个临时副本(用于差异),以及与数据长度相同的布尔数组(每个元素 1 位),它应该非常有效......
However, it does require a twice as much memory as the various generator-based solutions. As long as you can hold a single temporary copy of your data in memory (for the diff), and a boolean array of the same length as your data (1-bit-per-element), it should be pretty efficient...
import numpy as np
def main():
# Generate some random data
x = np.cumsum(np.random.random(1000) - 0.5)
condition = np.abs(x) < 1
# Print the start and stop indices of each region where the absolute
# values of x are below 1, and the min and max of each of these regions
for start, stop in contiguous_regions(condition):
segment = x[start:stop]
print start, stop
print segment.min(), segment.max()
def contiguous_regions(condition):
"""Finds contiguous True regions of the boolean array "condition". Returns
a 2D array where the first column is the start index of the region and the
second column is the end index."""
# Find the indicies of changes in "condition"
d = np.diff(condition)
idx, = d.nonzero()
# We need to start things after the change in "condition". Therefore,
# we'll shift the index by 1 to the right.
idx += 1
if condition[0]:
# If the start of condition is True prepend a 0
idx = np.r_[0, idx]
if condition[-1]:
# If the end of condition is True, append the length of the array
idx = np.r_[idx, condition.size] # Edit
# Reshape the result into two columns
idx.shape = (-1,2)
return idx
main()