ptp(a, axis=None)
This docstring was copied from numpy.ptp.
Some inconsistencies with the Dask version may exist.
The name of the function comes from the acronym for 'peak to peak'.
:None:None:`ptp` preserves the data type of the array. This means the return value for an input of signed integers with n bits (e.g. :None:None:`np.int8`, :None:None:`np.int16`, etc) is also a signed integer with n bits. In that case, peak-to-peak values greater than 2**(n-1)-1
will be returned as negative values. An example with a work-around is shown below.
Input values.
Axis along which to find the peaks. By default, flatten the array. :None:None:`axis` may be negative, in which case it counts from the last to the first axis.
If this is a tuple of ints, a reduction is performed on multiple axes, instead of a single axis or all the axes as before.
Alternative output array in which to place the result. It must have the same shape and buffer length as the expected output, but the type of the output values will be cast if necessary.
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 ptp
method of sub-classes of :None:None:`ndarray`, however any non-default value will be. If the sub-class' method does not implement keepdims
any exceptions will be raised.
A new array holding the result, unless :None:None:`out` was specified, in which case a reference to :None:None:`out` is returned.
Range of values (maximum - minimum) along an axis.
>>> x = np.array([[4, 9, 2, 10], # doctest: +SKIPThis example is valid syntax, but we were not able to check execution
... [6, 9, 7, 12]])
>>> np.ptp(x, axis=1) # doctest: +SKIP array([8, 6])This example is valid syntax, but we were not able to check execution
>>> np.ptp(x, axis=0) # doctest: +SKIP array([2, 0, 5, 2])This example is valid syntax, but we were not able to check execution
>>> np.ptp(x) # doctest: +SKIP 10
This example shows that a negative value can be returned when the input is an array of signed integers.
This example is valid syntax, but we were not able to check execution>>> y = np.array([[1, 127], # doctest: +SKIP
... [0, 127],
... [-1, 127],
... [-2, 127]], dtype=np.int8)
... np.ptp(y, axis=1) # doctest: +SKIP array([ 126, 127, -128, -127], dtype=int8)
A work-around is to use the :None:None:`view()` method to view the result as unsigned integers with the same bit width:
>>> np.ptp(y, axis=1).view(np.uint8) # doctest: +SKIP array([126, 127, 128, 129], dtype=uint8)See :
The following pages refer to to this document either explicitly or contain code examples using this.
dask.array.routines.ptp
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