How to get index of maximum value of each consecutive 4 numbers in a list of python?

Question

I have a list L. It has random numbers.

I want to get the index of maximum number among each 4 numbers of L.

What is the way to do it ?

I can get the max value from below (i guess ) but not sure how to get index value ? Also is there a way to do same in nd array ???

import pandas as pd
a=np.random.rand(100)
L=list(a)
pd.rolling_max(L, 4)

Just do a for loop, make an if statement to check whether the value equals the maximum number in the list, then use the index method for the value inside of the list. There are plenty of such basic tutorials on the web. — JackTheCrab, Nov 01 '16 at 20:02
See if this helps - http://stackoverflow.com/questions/16157913/rolling-idxmax-in-python — Divakar, Nov 01 '16 at 20:08
you may also want to check [this answer](http://stackoverflow.com/a/40101614/5741205) — MaxU - stand with Ukraine, Nov 01 '16 at 20:34
To asker : Linked dup has solutions using both pandas and numpy, so should solve your case. — Divakar, Nov 01 '16 at 20:36
`[max(enumerate(itertools.islice(a, i, i+4), start=i),key=lambda x:x[1])[0] for i in range(len(a)-4+1)]` — Steven Rumbalski, Nov 01 '16 at 20:49
Steven, this is not giving me index of max value among 4 consecutive numbers, I am trying to fix . Thanks — A. wadhawan, Nov 03 '16 at 09:39

score 0 · Answer 1 · answered Nov 01 '16 at 19:57

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There is no quicker way than to run through the list looking at the 4 size subsets. For each subset, you can have a variable that stores the index of the maximum number seen so far (among the 4). This is O(n) which is the quickest you can do it because you will have to look at each number in the list at least once.

answered Nov 01 '16 at 19:57

Riwaz Poudyal

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thanks, Can you please give example of this method – A. wadhawan Nov 01 '16 at 19:59
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This is a comment, not an answer. – Steven Rumbalski Nov 01 '16 at 20:09

How to get index of maximum value of each consecutive 4 numbers in a list of python?

1 Answers1