numpy.argmax — NumPy v1.18 Manual (original) (raw)

numpy. argmax(a, axis=None, out=None)[source]¶

Returns the indices of the maximum values along an axis.

Parameters

aarray_like

Input array.

axisint, optional

By default, the index is into the flattened array, otherwise along the specified axis.

outarray, optional

If provided, the result will be inserted into this array. It should be of the appropriate shape and dtype.

Returns

index_arrayndarray of ints

Array of indices into the array. It has the same shape as _a.shape_with the dimension along axis removed.

Notes

In case of multiple occurrences of the maximum values, the indices corresponding to the first occurrence are returned.

Examples

a = np.arange(6).reshape(2,3) + 10 a array([[10, 11, 12], [13, 14, 15]]) np.argmax(a) 5 np.argmax(a, axis=0) array([1, 1, 1]) np.argmax(a, axis=1) array([2, 2])

Indexes of the maximal elements of a N-dimensional array:

ind = np.unravel_index(np.argmax(a, axis=None), a.shape) ind (1, 2) a[ind] 15

b = np.arange(6) b[1] = 5 b array([0, 5, 2, 3, 4, 5]) np.argmax(b) # Only the first occurrence is returned. 1

x = np.array([[4,2,3], [1,0,3]]) index_array = np.argmax(x, axis=-1)

Same as np.max(x, axis=-1, keepdims=True)

np.take_along_axis(x, np.expand_dims(index_array, axis=-1), axis=-1) array([[4], [3]])

Same as np.max(x, axis=-1)

np.take_along_axis(x, np.expand_dims(index_array, axis=-1), axis=-1).squeeze(axis=-1) array([4, 3])