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Old 11-05-2008, 10:40 AM   #1
lighthousekeeper
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Join Date: Oct 2000
math problem: fuzzy system of linear equations

i've got a math problem and am struggling with coming up with an answer. i have a system of linear equations like:

ax + by + cz = 123456...
dx + ey + fz = 7890123...
gx + hy + iz = 456789...

(In my case, instead of a 3 x 3 matrix like the one above, it's an 8 by 8 matrix.) 8 equations, 8 unknowns. I know that if the 8 equations are "consistent", then an exact solution could be determined using linear algebra row reduction, Cramer's rule, or similar techniques.

BUt my problem is that the 8 equations are known to be inconsistent. In other words, ax+by+cz doesn't exactly equal 123456, but rather 123456 is some apprximation with an unknown accuracy.

I don't expect or want an exact answer to the 8 unknowns, but rather a range of values, or a statistical probability of answers. Any thoughts?
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Old 11-05-2008, 11:36 AM   #2
gstelmack
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Matlab? Maple? Mathcad?
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Old 11-05-2008, 11:39 AM   #3
johnnyshaka
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Nothing to add, I'll move along.
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Old 11-05-2008, 11:44 AM   #4
Dr. Sak
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Do you know how much the approximate values range?
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Old 11-05-2008, 12:02 PM   #5
twothree
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I think you would want to use Maximum likelihood estimation.

Maximum likelihood - Wikipedia, the free encyclopedia
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Old 11-05-2008, 12:24 PM   #6
lighthousekeeper
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Quote:
Originally Posted by twothree View Post
I think you would want to use Maximum likelihood estimation.

Maximum likelihood - Wikipedia, the free encyclopedia

thanks - i think this might be what i'm looking for (now i just need a couple years of advanced statistics training)
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Old 11-05-2008, 12:26 PM   #7
Toddzilla
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Maximum Likelihood - snicker....
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Old 11-05-2008, 12:59 PM   #8
RedHawk00
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if you have matlab or one of the free knockoffs, look up SVD (Singular Value Decomposition), this gives you a best estimation of the 8 unknown. Note: you can also feed it 8+ equations to give you best guess on the 8 unknowns
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