numpy.diff(a, n=1, axis=1, prepend=<no value>, append=<no value>)
[source]
Calculate the nth discrete difference along the given axis.
The first difference is given by out[i] = a[i+1]  a[i]
along the given axis, higher differences are calculated by using diff
recursively.
Parameters: 


Returns: 

Type is preserved for boolean arrays, so the result will contain False
when consecutive elements are the same and True
when they differ.
For unsigned integer arrays, the results will also be unsigned. This should not be surprising, as the result is consistent with calculating the difference directly:
>>> u8_arr = np.array([1, 0], dtype=np.uint8) >>> np.diff(u8_arr) array([255], dtype=uint8) >>> u8_arr[1,...]  u8_arr[0,...] 255
If this is not desirable, then the array should be cast to a larger integer type first:
>>> i16_arr = u8_arr.astype(np.int16) >>> np.diff(i16_arr) array([1], dtype=int16)
>>> x = np.array([1, 2, 4, 7, 0]) >>> np.diff(x) array([ 1, 2, 3, 7]) >>> np.diff(x, n=2) array([ 1, 1, 10])
>>> x = np.array([[1, 3, 6, 10], [0, 5, 6, 8]]) >>> np.diff(x) array([[2, 3, 4], [5, 1, 2]]) >>> np.diff(x, axis=0) array([[1, 2, 0, 2]])
>>> x = np.arange('10661013', '10661016', dtype=np.datetime64) >>> np.diff(x) array([1, 1], dtype='timedelta64[D]')
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https://docs.scipy.org/doc/numpy1.17.0/reference/generated/numpy.diff.html