How to get the index of a maximum element in a NumPy array along one axis

Question

I have a 2 dimensional NumPy array  I know how to get the maximum values over axes   gt  gt  gt  a   array   1 2 3   4 3 1     gt  gt  gt  amax a axis 0  array  4  3  3    How can I get the indices of the maximum elements  I would like as output array  1 1 0   instead

User · Answer

gt  gt  gt  import numpy as np  gt  gt  gt  a   np array   1 2 3   4 3 1     gt  gt  gt  i j   np unravel index a argmax    a shape   gt  gt  gt  a i j  4

User · Answer

v   alli max   index   alli argmax   x  y   index 8  index 8

User · Answer

There is argmin   and argmax   provided by numpy that returns the index of the min and max of a numpy array respectively  Say e g for 1-D array you ll do something like this  x000D   x000D  import numpy as np  a   np array  50 1 0 2    print a argmax      returns 0 print a argmin      returns 2 x000D   x000D   x000D   And similarly for multi-dimensional array  x000D   x000D  import numpy as np  a   np array   0 2 3   4 30 1     print a argmax      returns 4 print a argmin      returns 0 x000D   x000D   x000D    Note that these will only return the index of the first occurrence

User · Answer

gt  gt  gt  a argmax axis 0   array  1  1  0

User · Answer

argmax   will only return the first occurrence for each row  http   docs scipy org doc numpy reference generated numpy argmax html  If you ever need to do this for a shaped array  this works better than unravel   import numpy as np a   np array   1 2 3    4 3 1       Can be of any shape indices   np where a    a max      You can also change your conditions   indices   np where a  gt   1 5    The above gives you results in the form that you asked for  Alternatively  you can convert to a list of x y coordinates by   x y coords    zip indices 0   indices 1

[python] How to get the index of a maximum element in a NumPy array along one axis

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