On Tue, Sep 13, 2011 at 3:34 PM, Ralf Gommers <ralf.gomm...@googlemail.com>wrote:
> Hi Jacob, > > On Fri, Sep 9, 2011 at 11:57 PM, Jacob Silterra <jsil...@gmail.com> wrote: > >> Hello all, >> >> I'd like to see functions for calculating the relative extrema in a set of >> data included in numpy. I use that functionality frequently, and always seem >> to be writing my own version. It seems like this functionality would be >> useful to the community at large, as it's a fairly common operation. >> > > What is your application? > >> >> For numeric data (which is presumably noisy), the definition of a relative >> extrema isn't completely obvious. The implementation I am proposing finds a >> point in an ndarray along an axis which is larger (or smaller) than it's >> `order` nearest neighbors (`order` being an optional parameter, default 1). >> This is likely to find more points than may be desired, which I believe is >> preferable to the alternative. The output is formatted the same as >> numpy.where. >> >> Code available here: https://github.com/numpy/numpy/pull/154 >> >> I'm not sure whether this belongs in numpy or scipy, that question is >> somewhat debatable. More sophisticated peak-finding functions (in N >> dimensions, as opposed to 1) may also be useful to the community, and those >> would definitely belong in scipy. >> > > I have the feeling this belongs in scipy. Although if it's just these two > functions I'm not sure where exactly to put them. Looking at the > functionality, this is quite a simple approach. For any data of the type I'm > usually working with it will not be able to find the right local extrema. > The same is true for your alternative definition below. > > A more powerful peak detection function would be a very good addition to > scipy imho (perhaps in scipy.interpolate?). See also > http://stackoverflow.com/questions/1713335/peak-finding-algorithm-for-python-scipy > > Cheers, > Ralf > > Actually, such an algorithm would be great to partner with the watershed clustering implementation in ndimage. Ben Root
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