熊猫系列累积argmax

Question

What is an efficient way to get a series of the cumulative argmax of another series?

The way I figured is

import pandas as pd

def cumargmax(series):
    return pd.expanding_apply(series, lambda x: x.argmax())

This works, but I'm wondering if there is a more appropriate way.

Answer 1

You don't need cumargmax function. Instead, you could do this in one line,

pd.expanding_apply(series, lambda x: x.argmax())

pandas 0.18 is deprecating expanding_apply() module level funtions. They are replacing with the following method call,

series.expanding().apply(lambda x: x.argmax())

Check out documentation at http://pandas.pydata.org/pandas-docs/stable/computation.html