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problem with consistency of root finding and sorting
From: |
Ben Abbott |
Subject: |
problem with consistency of root finding and sorting |
Date: |
Tue, 9 Oct 2007 19:57:00 -0400 |
I have Octave 2.9.14 on Mac OS X (intel & PPC) installed via Fink and
am concerned that my installations are giving different results than
others.
During the process of modifying residue.m so that it would function
in a manner consistent with Matlab's I've become suspicious that my
Octave installation does not work the same as others.
The difference is small, but is troublesome.
Given the following short example,
r = sort(roots([1 0 18 0 81]))
r_err = r - round(r)
I obtain the results below
r = sort(roots([1 0 18 0 81]))
r =
0.0000 - 3.0000i
0.0000 + 3.0000i
-0.0000 - 3.0000i
-0.0000 + 3.0000i
r_err = r - round(r)
r_err =
2.5814e-08 + 1.6920e-08i
2.5814e-08 - 1.6920e-08i
-2.5814e-08 - 1.6920e-08i
-2.5814e-08 + 1.6920e-08i
I suspect that others are getting slightly different results.
Specifically, some installations appear to be returning conjugate of
"r" instead. I've posted the "r_err" because it appears larger than
I'd expect.
I'd appreciate if others would try to short script and post the
result ... in the hope of isolating the problem.
TiA
- problem with consistency of root finding and sorting,
Ben Abbott <=
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/09
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/09
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/09
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/09
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10
- Re: problem with consistency of root finding and sorting, David Bateman, 2007/10/10
- Re: problem with consistency of root finding and sorting, Ben Abbott, 2007/10/10