Get array with maximum value for each array index

Question

I am using Python 3 on CentOS 7. I would like to find the quickest way to get the index of the array with the maximum, for each index with the arrays, over multiple arrays without using loops. For example, if I input

array[0] = [1,3,9,4,6,8,9] array[1] = [2,6,3,8,7,4,5] array[2] = [6,3,7,9,1,3,6]

I would like the output to be

[2,1,0,2,1,0,0]

I tried

np.maximum.reduce(array)

and got the maximum values, across the arrays, for the indices across arrays. However, when I tried

array.index(np.maximum.reduce(array))

I get

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Andrea Grioni · Accepted Answer · 2019-11-01 21:49:49Z

2

Try with argmax from numpy

np.argmax(array, axis = 1)

output

[2 3 3]

answered Nov 1, 2019 at 21:49

Andrea Grioni

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1 Comment

OtagoHarbour Over a year ago

That worked, except I had to use axis = 0. Thank very much!

Bill Chen · Accepted Answer · 2019-11-01 21:47:42Z

1

Try this:

import numpy as np
import pandas as pd
arr = np.array([[1,3,9,4,6,8,9],
        [2,6,3,8,7,4,5],
        [6,3,7,9,1,3,6]])

df = pd.DataFrame(arr)

print(df)

result = [df[x].idxmax() for x in df]
print(result)

answered Nov 1, 2019 at 21:47

Bill Chen

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