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

Question

I have a two-dimensional NumPy array. I know how to get the maximum values ​​along the axes:

>>> a = array([[1,2,3],[4,3,1]]) >>> amax(a,axis=0) array([4, 3, 3]) 

How can I get the indices of the maximum elements? So I would like to get the output of array([1,1,0])

Answer 1

 >>> a.argmax(axis=0) array([1, 1, 0]) 

Answer 2

 >>> import numpy as np >>> a = np.array([[1,2,3],[4,3,1]]) >>> i,j = np.unravel_index(a.argmax(), a.shape) >>> a[i,j] 4 

Answer 3

argmax() returns only the first occurrence for each row. http://docs.scipy.org/doc/numpy/reference/generated/numpy.argmax.html

If you need to do this for an array in the form, 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 >= 1.5) 

The above results give the form in the requested form. In addition, you can convert to a list of x, y coordinates by:

 x_y_coords = zip(indices[0], indices[1]) 

Answer 4

 v = alli.max() index = alli.argmax() x, y = index/8, index%8