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odd griddata error message
From: |
Søren Hauberg |
Subject: |
odd griddata error message |
Date: |
Tue, 13 Jun 2006 23:03:56 +0200 |
Hi,
I'm using griddata from octave-forge in octave 2.1.72 to interpolate
unevenly spaced data. However, I get the following long error message
from QHull. I don't know what this message means, so if anybody has some
insight I would be very interested...
Søren
qhull precision error: initial simplex is not convex. Distance=2.1e-17
While executing: | qhull d Qbb T0
Options selected for Qhull 2003.1 2003/12/30:
delaunay Qbbound-last _pre-merge _zero-centrum Pgood _max-width
1.6e+02
Error-roundoff 2.2e-13 _one-merge 1.6e-12 _near-inside 7.8e-12
Visible-distance 4.4e-13 U-coplanar-distance 4.4e-13 Width-outside
8.9e-13
_wide-facet 2.7e-12
The input to qhull appears to be less than 3 dimensional, or a
computation has overflowed.
Qhull could not construct a clearly convex simplex from points:
- p588 (v3): 1.2e+02 1.6e+02 1.6e+02
- p469 (v2): 1 1.6e+02 1e+02
- p119 (v1): 1.2e+02 1 57
- p0 (v0): 1 1 5.6e-19
The center point is coplanar with a facet, or a vertex is coplanar
with a neighboring facet. The maximum round off error for
computing distances is 2.2e-13. The center point, facets and distances
to the center point are as follows:
center point 60.5 80.5 79.5
facet p469 p119 p0 distance= -4.4e-15
facet p588 p119 p0 distance= -4.4e-15
facet p588 p469 p0 distance= -7.7e-15
facet p588 p469 p119 distance= -7.7e-15
These points either have a maximum or minimum x-coordinate, or
they maximize the determinant for k coordinates. Trial points
are first selected from points that maximize a coordinate.
The min and max coordinates for each dimension are:
0: 1 120 difference= 119
1: 1 160 difference= 159
2: 5.565e-19 159 difference= 159
If the input should be full dimensional, you have several options that
may determine an initial simplex:
- use 'QJ' to joggle the input and make it full dimensional
- use 'QbB' to scale the points to the unit cube
- use 'QR0' to randomly rotate the input for different maximum points
- use 'Qs' to search all points for the initial simplex
- use 'En' to specify a maximum roundoff error less than 2.2e-13.
- trace execution with 'T3' to see the determinant for each point.
If the input is lower dimensional:
- use 'QJ' to joggle the input and make it full dimensional
- use 'Qbk:0Bk:0' to delete coordinate k from the input. You should
pick the coordinate with the least range. The hull will have the
correct topology.
- determine the flat containing the points, rotate the points
into a coordinate plane, and delete the other coordinates.
- add one or more points to make the input full dimensional.
This is a Delaunay triangulation and the input is co-circular or
co-spherical:
- use 'Qz' to add a point "at infinity" (i.e., above the paraboloid)
- or use 'QJ' to joggle the input and avoid co-circular data
error: invalid column index = 2
error: evaluating argument list element number 1
error: evaluating assignment expression near line 75, column 7
error: evaluating if command near line 55, column 3
error: called from `griddata' in file
`/usr/share/octave/site/m/octave-forge/geometry/griddata.m'
error: evaluating assignment expression near line 101, column 15
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