numpy.
amax
(a, axis=None, out=None, keepdims=<no value>, initial=<no value>, where=<no value>)[source]¶
Return the maximum of an array or maximum along an axis.
Parameters:Input data.
Axis or axes along which to operate. By default, flattened input is used.
New in version 1.7.0.
If this is a tuple of ints, the maximum is selected over multiple axes, instead of a single axis or all the axes as before.
Alternative output array in which to place the result. Must be of the same shape and buffer length as the expected output. See doc.ufuncs
(Section âOutput argumentsâ) for more details.
If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.
If the default value is passed, then keepdims will not be passed through to the amax
method of sub-classes of ndarray
, however any non-default value will be. If the sub-classâ method does not implement keepdims any exceptions will be raised.
The minimum value of an output element. Must be present to allow computation on empty slice. See reduce
for details.
New in version 1.15.0.
Elements to compare for the maximum. See reduce
for details.
New in version 1.17.0.
Maximum of a. If axis is None, the result is a scalar value. If axis is given, the result is an array of dimension a.ndim - 1
.
See also
amin
nanmax
maximum
fmax
argmax
Notes
NaN values are propagated, that is if at least one item is NaN, the corresponding max value will be NaN as well. To ignore NaN values (MATLAB behavior), please use nanmax.
Donât use amax
for element-wise comparison of 2 arrays; when a.shape[0]
is 2, maximum(a[0], a[1])
is faster than amax(a, axis=0)
.
Examples
>>> a = np.arange(4).reshape((2,2)) >>> a array([[0, 1], [2, 3]]) >>> np.amax(a) # Maximum of the flattened array 3 >>> np.amax(a, axis=0) # Maxima along the first axis array([2, 3]) >>> np.amax(a, axis=1) # Maxima along the second axis array([1, 3]) >>> np.amax(a, where=[False, True], initial=-1, axis=0) array([-1, 3]) >>> b = np.arange(5, dtype=float) >>> b[2] = np.NaN >>> np.amax(b) nan >>> np.amax(b, where=~np.isnan(b), initial=-1) 4.0 >>> np.nanmax(b) 4.0
You can use an initial value to compute the maximum of an empty slice, or to initialize it to a different value:
>>> np.max([[-50], [10]], axis=-1, initial=0) array([ 0, 10])
Notice that the initial value is used as one of the elements for which the maximum is determined, unlike for the default argument Pythonâs max function, which is only used for empty iterables.
>>> np.max([5], initial=6) 6 >>> max([5], default=6) 5
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