[SciPy-User] [SciPy-user] Selection of dominant points

Joe Kington jkington@wisc....
Sat Jul 25 02:02:33 CDT 2009


Well, I thought shapely <http://trac.gispython.org/lab/wiki/Shapely> would
have some sort of line-generalization capabilities, but apparently it
doesn't.

You may already be aware of this, but algorithm wise, you're looking for the
Douglas-Peucker
algorithm<http://en.wikipedia.org/wiki/Ramer-Douglas-Peucker_algorithm>,
or something similar.

If you don't want to mess with implementing it yourself, you might want to
look at grass <http://grass.itc.it/>.  Grass has a
generalize<http://grass.osgeo.org/wiki/V.generalize_tutorial>function
that should do what you need, and does have at least some python
bindings.  I've never actually used the python bindings for
grass<http://download.osgeo.org/grass/grass6_progman/pythonlib.html>,
so I can't help you too much there...

Hope that helps, at any rate!
-Joe

On Fri, Jul 24, 2009 at 11:45 PM, David Warde-Farley <dwf@cs.toronto.edu>wrote:

> On 24-Jul-09, at 11:47 AM, Charles Vejnar wrote:
>
> > Hi,
> >
> > I have a curve with millions of points which is non-standard (i.e.
> > it's not a
> > gaussian or ...).
> >
> > I would like to select about 500 points which best describe the curve
> > (something like selecting dominant points).
>
> It would be helpful to know more about the problem.  Like:
> - are the points evenly spaced along the independent axis?
> - are they assumed to be samples from a continuous signal?
> - does the signal have any known structure at all? If you could
> describe where these data come from it might help nail down what
> methods would be appropriate.
>
> Regards,
>
> David
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