numpy array iteration to track maximum number so far

Question

Is there a simple way of iterating through a two dimensional array to store maximum value obtained so far while traversing along a particular dimension. For example, i have an array:

[[2 ,  1,  5],
[-1, -1,  4],
[4, 3,  2],
[2 , 3, 4]]

and I would like the following output:

[[2 ,  2,  5],
[-1, -1,  4],
[4, 4,  4],
[2 , 3, 4]]

Thanks!

senderle · Accepted Answer · 2012-07-09 20:46:02Z

5

Easy; use accumulate:

>>> numpy.maximum.accumulate(a, axis=1)
array([[ 2,  2,  5],
       [-1, -1,  4],
       [ 4,  4,  4],
       [ 2,  3,  4]])

answered Jul 9, 2012 at 20:46

senderle

152k36 gold badges218 silver badges244 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

GL770 · Accepted Answer · 2012-07-09 18:52:38Z

0

If computation time is not an issue, you can do something like:

my_new_array = [ [max(my_array[i][:j+1]) for j in range(len(my_array[i]))] for i in range(len(my_array))]

However it is really not computation-time efficient. It would probably be much more efficient to do 2 loops.

answered Jul 9, 2012 at 18:52

GL770

3,2701 gold badge16 silver badges9 bronze badges

1 Comment

user1512829 Over a year ago

Thanks..I will probably go with using loops.

Collectives™ on Stack Overflow

numpy array iteration to track maximum number so far

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related