How do we split a python list at the largest gap, given kth times?-CodePudding

Given a list:

data = [71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51, 86.82, 87.81, 87.87, 146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]

how do we write a function with two variable (data, and k). data would be a 1d array of floating numbers and k would be the amount of list we intend to return.

for example using the list given above:

this is our function separate(data, 2) should return -> [[71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51, 86.82, 87.81, 87.87] , [146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]]

separate(data, 1) should return -> [[71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51, 86.82, 87.81, 87.87, 146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]]

separate(data, 3) should return -> [[71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51], [86.82, 87.81, 87.87] , [146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]]

CodePudding user response：

Step 1: Compute the gap sized and their positions:

gaps = [(q - p, pos) for pos, (p, q) in enumerate(pairwise(data))]

Step 2: Extract the k-largest gaps:

large_gaps = largest(k-1, gaps)

Step 3: Use the positions to split the data

The imports are:

from itertools import pairwise
from heapq import nlargest

CodePudding user response：

If data is your initial list from the question, you can do:

N = 3

gaps = sorted(
    [(i, abs(a - b)) for i, (a, b) in enumerate(zip(data, data[1:]))],
    key=lambda k: -k[1],
)[: N - 1]

out, prev = [], 0
for idx, _ in sorted(gaps):
    out.append(data[prev : idx   1])
    prev = idx   1

if prev < len(data):
    out.append(data[prev:])

print(out)

Prints:

[[71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51], [86.82, 87.81, 87.87], [146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]]

For N = 2:

[[71.4, 72.73, 74.36, 75.38, 76.15, 76.96, 79.51, 86.82, 87.81, 87.87], [146.38, 150.89, 151.16, 152.18, 152.36, 153.27, 155.7, 160.99, 161.36, 164.55]]