## RE: AI-GEOSTATS: singular matrix during conditional simulation

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• I do not anything about GSLIB, but when two rows or cols in a matrix are identical, the determinant of the matrix is zero. A matrix is called singular when its
Message 1 of 2 , Jul 15, 2003
I do not anything about GSLIB, but when two rows or cols in a matrix are
identical, the determinant of the matrix is zero. A matrix is called
singular when its det. is zero. A singular matrix cannot be inverted.

Note that it is also possible for the product of two matrices to have a zero
determinant, without each of them being zero.

Rajive Ganguli, Ph.D., P.E., C.O.I
Associate Professor of Mining Engineering
=====
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> -----Original Message-----
> From: ai-geostats-list@... [mailto:ai-geostats-list@...]On
> Behalf Of Ulrich Leopold
> Sent: Tuesday, July 15, 2003 3:25 AM
> To: ai-geostats@...
> Subject: AI-GEOSTATS: singular matrix during conditional simulation
>
>
> Dear list,
>
> I encounter a problem in Gstat. I posted my message to the
> Gstat list but get currently no answer.
> Maybe someone here experienced this problem already in Gstat
> or has any ideas how to solve it:
>
> Gstat terminates with the message "matrix library error: singular
> matrix" (see below). The trouble shooting in the manual says:
> Increase the value of zero.
> I did that. Nothing changes. Another solution is to average
> values at identical locations.
> I did that as well with the average option in data().
>
> I had a look to the debug file but do not quite get a clue
> from it except that the last matrix
> has 2 identical columns?? That's when Gstat stops. You can
> find that matrix below as well.
> Any ideas how to solve this problem?
>
> Ulrich
>
> ---------------------------------------------------------------
>
> gstat: Linux version 2.4.2 (26 April 2003)
> Copyright (C) 1992, 2003 Edzer J. Pebesma
> using Marsaglia's random number generator
>
> [using conditional gaussian simulation]
> initializing maps .
> 0% done
> "chfactor.c", line 130: singular matrix in function LDLfactor()
>
> gstat caught an error that occurred in the matrix library,
> the reason for it was: singular matrix
>
> HINT: Read the manual (http://www.geog.uu.nl/gstat/manual)
> look for: Trouble shooting -> Error messages -> From meschach
>
> gstat: matrix library error: singular matrix
>
> --------------------------------------------------------------------
>
> idx x:;y:;z:;v:;
> 0 x: 254083 y: 552263 z: 0 weight: 1
>
> # Covariances (x_i, x_j) matrix C (lower triangle only):
> Matrix: 10 by 10
> row 0: 174.0506 0 0 0
> 0 0 0 0
> 0
> 0
> row 1: 174.0506 174.0506 0 0
> 0 0 0 0
> 0
> 0
> row 2: 45.0007921 45.0007921 174.0506 0
> 0 0 0 0
> 0
> 0
> row 3: 43.8068348 43.8068348 37.2124655 174.0506
> 0 0 0 0
> 0
> 0
> row 4: 43.4219499 43.4219499 36.9949687 52.578787
> 174.0506 0 0 0
> 0
> 0
> row 5: 40.3552653 40.3552653 36.7606584 43.6115366
> 44.1867844 52.612507 0 0
> 0
> 0
> row 6: 38.927339 38.927339 42.9203931 34.49808
> 34.5784392 38.2033244 52.612507 0
> 0
> 0
> row 7: 45.4024655 45.4024655 38.5251957 45.9125721
> 45.1916088 38.2033244 33.2536242 52.612507
> 0
> 0
> row 8: 43.4915577 43.4915577 36.7949906 52.0550197
> 51.3836065 42.5157124 33.7749338 46.6269808
> 174.0506
> 0
> row 9: 40.7441753 40.7441753 48.2783442 33.6299795
> 33.4342596 33.6128998 42.2386301 35.0813766
> 33.260144
> 174.0506
>
> --------------------------------------------------------------
> ---------------
>
>
> --
> __________________________________________________
>
> Ulrich Leopold MSc.
>
> Department of Physical Geography
> Institute for Biodiversity and Ecosystem Dynamics
> Faculty of Science
> University of Amsterdam
> Nieuwe Achtergracht 166
> NL-1018WV Amsterdam
>
> Phone: +31-(0)20-525-7456 (7451 Secretary)
> Fax: +31-(0)20-525-7431
> Email: uleopold@...
> http://www.frw.uva.nl/soil/Welcome.html
>
> Check us also out at:
> Netherlands Centre for Geo-ecological Research
> http://www.frw.uva.nl/icg
>
>
>
>
>
> --
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