Re: qhull internal error.

[Philip Hahn]

I should add that it works fine in 3.2 if you take the "cubic" option
out of griddata.

philip

On Wed, Oct 19, 2011 at 4:34 PM, Philip Hahn <address@hidden> wrote:
> 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
>