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Re: diagonal dominant [message #84716 is a reply to message #83035]

Wed, 30 January 2013 19:36

Gompie
Messages: 76
Registered: August 2012

Member

Let me pose the question in better words.

I want to get the value of X in AX=B. Since X has 256 unknowns, I have selected 256 rows of A from a database of many rows which i can generate by increasing the input range of my model. This selection is done after removing duplicate rows because duplicate rows will make matrix A singular.

So I have the flexibility of choosing any 256 non duplicate rows which can work best for me. I am not removing identical columns in this problem.

By noisy i mean two things.
1. The solution is large error bars
2. A slight change in B ( without any change in A) makes the solution. This means that condition number of A should be ok and that it should be invertible

So the problem now is how make a selection so that A is invertible. But before that in idl when I give determ(A) it get 0.0000 Floating point error. So I am not sure if determinant is properly calulated A inverse is anyway wrong.

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[Message index]

		diagonal dominant By: Gompie on Wed, 30 January 2013 06:26
		Re: diagonal dominant By: Mats Löfdahl on Thu, 31 January 2013 05:26
		Re: diagonal dominant By: Gompie on Thu, 31 January 2013 05:05
		Re: diagonal dominant By: Mats Löfdahl on Thu, 31 January 2013 00:09
		Re: diagonal dominant By: Gompie on Wed, 30 January 2013 22:33
		Re: diagonal dominant By: Mats Löfdahl on Wed, 30 January 2013 15:13
		Re: diagonal dominant By: Gompie on Wed, 30 January 2013 19:36
		Re: diagonal dominant By: Gompie on Wed, 30 January 2013 09:21
		Re: diagonal dominant By: bstecklu on Wed, 30 January 2013 09:06
		Re: diagonal dominant By: Brian Daniel on Wed, 30 January 2013 09:00

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