Re: Voronoi Diagrams

[David Bateman]

Ben Abbott wrote:
> On Dec 22, 2008, at 1:43 PM, Søren Hauberg wrote:
>
>   
> > man, 22 12 2008 kl. 13:25 -0500, skrev Ben Abbott:
> >     
> > >         ll = min (length (idx), length (c));
> > >       
> > Isn't that the same as
> >
> >  ll = length (c);
> >
> > ?
> >
> > Søren
> >
> >     
>
> In this case yes. But I don't understand what the line below is  
> accounting for.
>
>         idx = find (!infi);
>
> Ben
>   

I suspect the issue is my fault and not Kai's ... When importing this 
code from octave-forge into Octave I tried to make it fully matlab 
compatible. Matlab draws lines in the Voronoi diagram with vertices at 
infinite, whereas the original octave-forge code didn't.. The get this 
behavior I added a big box around the vertices to simulate vertices at 
infinite, and then flagged the tesselations with a vertex at infinite 
with the third return argument of __voronoi__.. However I sized this 
return argument differently than the second return argument.. I suspect 
the attached is a better solution to the issue, though your proposed fix 
comes to much the same thing.. My patch tries to be a bit faster as it 
avoid multiple resizes of one of the return arrays as well.

D.



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# HG changeset patch
# User David Bateman <address@hidden>
# Date 1229980587 -3600
# Node ID 9802e81c317a0772404ff54ea0a16e91b7f7d9f7
# Parent  777fcb8a9da08541a3043dc489faae326c239880
Reszie third arg of __voronoi__ before retuning it

diff --git a/src/ChangeLog b/src/ChangeLog
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2008-12-22  David Bateman  <address@hidden>
+
+       * DLD-FUNCTIONS/__voronoi__.cc (F__voronoi__): Resize AtInf array
+       before returning it.
+
 2008-12-12  David Bateman  <address@hidden>
 
        * DLD-FUNCTIONS/chol.cc (Fcholinv): Add test.
diff --git a/src/DLD-FUNCTIONS/__voronoi__.cc b/src/DLD-FUNCTIONS/__voronoi__.cc
--- a/src/DLD-FUNCTIONS/__voronoi__.cc
+++ b/src/DLD-FUNCTIONS/__voronoi__.cc
@@ -165,7 +165,7 @@
       boolMatrix AtInf (np, 1);
       for (i = 0; i < np; i++) 
        AtInf(i) = false;
-      octave_value_list F;
+      octave_value_list F (np, octave_value ());
       k = 0;
       i = 0;
 
@@ -220,6 +220,7 @@
 
       retval(0) = v;
       retval(1) = C;
+      AtInf.resize (r, 1);
       retval(2) = AtInf;
 
       // free long memory