0

I have a numpy.array of data called f, I know the max value in it is f_max=max(f) but I would like to know the index in the array corresponding to the maximum value.

I tried:

count = 0
while (f[count]!=fmax)
    conto ++

but I receive an error: 

SyntaxError: invalid syntax

Could anyone help me?

Improve this question
3
  • On the syntax error: you need a : at the end of the while statement, and use count += 1, but the answer below is the right way to do it. Commented May 24, 2014 at 17:32
  • @Caos note that I have edited your question and included the numpy tag based on the information below that you are using a numpy array. If this information is incorrect then please say so. Commented May 24, 2014 at 17:38
  • Yes! I confirm that I was using a numpy array Commented May 24, 2014 at 19:02

2 Answers 2

Reset to default
4

If you're already using numpy, you can do this with argmax().

import numpy as np
a = np.array([1, 5, 2, 6, 3])

index = a.argmax()
Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

1

The easiest way would be to find the max and then, look for its index.

>>> a = [1, 5, 2, 3, 4]
>>> val = max(a)
>>> a.index(val)
1

You could also use enumerate to get a list of indices and the values corresponding to them and choose the max among them.

>>> list(enumerate(a))
[(0, 1), (1, 5), (2, 2), (3, 3), (4, 4)]
>>> index, _ = max(enumerate(a), key = lambda x: x[1])
>>> index
1
Improve this answer

5 Comments

Doing this I receive: 'numpy.ndarray' object has no attribute 'index'
@Caos: You should have mentioned you have a Numpy Array.
@Caos: You should use np.argmax in that case.
Sorry I am new to python ad I thought I was using a list
This solution only works to show the first instance of a max, is there a more robust solution?

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.