qhull internal error.

[Philip Hahn]

Hello,

 I am trying to create a contour plot of some irregular data. I have
the X, Y coordinates and the value of Z at each coordinate.

 I tried following the example code given at
http://blogs.mathworks.com/pick/2007/11/02/advanced-matlab-surface-plot-of-nonuniform-data/,
which is transcribed as follows:

*****CODE*****
x=rand(100,1)*16-8;
y=rand(100,1)*16-8;
r = sqrt(x.^2 + y.^2) + eps;
z = sin(r)./r;

xlin = linspace(min(x), max(x), 33);
ylin = linspace(min(y), max(y), 33);
[X,Y] = meshgrid(xlin, ylin);

Z = griddata(x,y,z, X,Y, 'cubic');

mesh(X,Y,Z);
axis tight;
hold on;
plot3(x,y,z,'.','MarkerSize',15);
*****CODE*****

When I run it in Octave 3.4.2, I get the following error:

qhull internal error (qh_qhull): temporary sets not empty (2)

While executing:  | qhull d Qt Qbb Qc
Options selected for Qhull 2009.1 2009/06/14:
  delaunay  Qtriangulate  Qbbound-last  Qcoplanar-keep  _pre-merge
  _zero-centrum  Pgood  Qinterior-keep  _max-width 16  Error-roundoff 2.2e-14
  _one-merge 1.5e-13  Visible-distance 4.4e-14  U-coplanar-distance 4.4e-14
  Width-outside 8.8e-14  _wide-facet 2.6e-13
Last point added to hull was p44.

At error exit:

Delaunay triangulation by the convex hull of 100 points in 3-d:

  Number of input sites: 100
  Number of Delaunay regions: 0

Statistics for:  | qhull d Qt Qbb Qc

  Number of points processed: 100
  Number of hyperplanes created: 507
  Number of facets in hull: 196
  Number of distance tests for qhull: 1795

error: __delaunayn__: qhull failed
error: called from:
error:   /usr/local/share/octave/3.4.2/m/geometry/delaunayn.m at line
56, column 5
error:   /usr/local/share/octave/3.4.2/m/geometry/delaunay.m at line
56, column 11
error:   /usr/local/share/octave/3.4.2/m/geometry/griddata.m at line
80, column 5
error:   /home/hahnpv/surfplot.m at line 10, column 3
octave:35> surfplot
qhull internal error (qh_qhull): temporary sets not empty (2)

While executing:  | qhull d Qt Qbb Qc
Options selected for Qhull 2009.1 2009/06/14:
  delaunay  Qtriangulate  Qbbound-last  Qcoplanar-keep  _pre-merge
  _zero-centrum  Pgood  Qinterior-keep  _max-width 16  Error-roundoff 2.2e-14
  _one-merge 1.5e-13  Visible-distance 4.4e-14  U-coplanar-distance 4.4e-14
  Width-outside 8.8e-14  _wide-facet 2.6e-13
Last point added to hull was p6.

At error exit:

Delaunay triangulation by the convex hull of 100 points in 3-d:

  Number of input sites: 100
  Number of Delaunay regions: 0

Statistics for:  | qhull d Qt Qbb Qc

  Number of points processed: 100
  Number of hyperplanes created: 496
  Number of facets in hull: 196
  Number of distance tests for qhull: 1709

error: __delaunayn__: qhull failed
error: called from:
error:   /usr/local/share/octave/3.4.2/m/geometry/delaunayn.m at line
56, column 5
error:   /usr/local/share/octave/3.4.2/m/geometry/delaunay.m at line
56, column 11
error:   /usr/local/share/octave/3.4.2/m/geometry/griddata.m at line
80, column 5
error:   /home/hahnpv/surfplot.m at line 10, column 3

...

any ideas? If there is a different approach I should be taking let me know.

Thanks,

Philip