[SciPy-user] probably a stupid question: MatLab equivalent of "diff" ?

Tom Denniston tom.denniston at alum.dartmouth.org
Fri Dec 29 09:35:08 CST 2006


I may be misunderstanding you but isn't what you want just:

arr[1:]-arr[:-1]

If you only want positive differences it's:

(arr[1:]-arr[:-1]) > 0

or negative:

(arr[1:]-arr[:-1]) < 0

These should be very fast.

--Tom


On 12/29/06, Stef Mientki <s.mientki at ru.nl> wrote:
> Does anyone know the equivalent of the MatLab "diff" function.
> The "diff" functions calculates the difference between 2 succeeding
> elements of an array.
> I need to detect (fast) the falling edge of a binary signal.
>
> There's derivate function in Python diff,
> but when you use an binary (true/false) input,
> it also detects rising edges.
>
> Probably a stupid question,
> but I still have troubles,
> digging to huge amount of information about Python.
>
> thanks,
> Stef Mientki
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