[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Octave-bug-tracker] [bug #54896] voronoi produces no edges for provided

From: Rik
Subject: [Octave-bug-tracker] [bug #54896] voronoi produces no edges for provided data
Date: Wed, 31 Oct 2018 00:42:59 -0400 (EDT)
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:63.0) Gecko/20100101 Firefox/63.0

Update of bug #54896 (project octave):

                Category:               Libraries => Octave Function        
                 Release:                   4.2.1 => dev                    


Follow-up Comment #6:

As I understand it, Matlab still uses QHull.  It just doesn't expose the API
to programmers anymore.  With Matlab, you are stuck using whatever options
they think are appropriate.

But, I don't think this is a problem with the QHull library.  The voronoi
function in voronoi.m does post-processing on the edges found.  I think there
may be an issue there.  The code is

  if (numel (x) > 2)
    ## Eliminate the edges of the diagram representing the box.
    ## Exclude points outside a certain radius from the center of
    ## FIXME: Factor should be at least 1.0.  Octave uses 1.1 for margin.
    ## There is no theoretical justification for this choice.
    ctr = [(xmax + xmin)/2 , (ymax + ymin)/2];
    radius = 1.1 * sumsq ([xmin, ymin] - ctr);
    dist = sumsq (p - ctr, 2);

    p_inside = (1:rows (p))(dist < radius);
    edge_inside = any (ismember (edges, p_inside));
    edges = edges(:, edge_inside);

If I change the factor from 1.1 to 100.1 then I get a figure equivalent to
Matlab.  If I comment out the code completely I get an en equivalent figure as


Reply to this item at:


  Message sent via Savannah

reply via email to

[Prev in Thread] Current Thread [Next in Thread]