       Re: What function to use to find matrix condition number?

• To: mathgroup at smc.vnet.net
• Subject: [mg114415] Re: What function to use to find matrix condition number?
• From: Oliver Ruebenkoenig <ruebenko at wolfram.com>
• Date: Fri, 3 Dec 2010 06:30:44 -0500 (EST)
• References: <201012031022.FAA20405@smc.vnet.net>

```
Hi Nasser,

On Fri, 3 Dec 2010, Nasser M. Abbasi wrote:

> This is version 8:
>
> I'd like to use LinearAlgebra`MatrixConditionNumber to find
> condition number of some matrix.
>
> btw, This command lists the functions in linear algebra.
> Names["LinearAlgebra`*"]
>
> But Mathematica says this package is now obsolete, and
> functionality is now in the kernel.
>
> <<LinearAlgebra`
> General::obspkg: {At Line = 3, the input was:,
> <<LinearAlgebra`,LinearAlgebra`} is now obsolete. The
> legacy version being loaded may conflict with current
> Mathematica functionality. See the Compatibility Guide for
> updating information. >>
>
> But When I follow the above, I get to page, where at the bottom
> it shows 3 functions, one of them is MatrixConditionNumber,
> but it does not show what replaced it in the kernel, instead
> it points to a link to MathSource article:
>
> "These functions were available in previous versions of Mathematica
> and are now available on the web at
> library.wolfram.com/infocenter/MathSource/6770"
>
> ?
>
> So, is there no build-in function to compute condition number now
> in Mathematica?
>

I made the suggestion that MatrixConditionNumber become a true kernel
function.

I still use the LinearAlgebra`MatrixConditionNumber to find the condition
number.

> I know I can find the max eigenvalue, divide it by the min
> eigenvalue (absolute values), and this gives me the condition
> number. But should not such a function be part of the system?
>

Yes, I agree.

Oliver

> Or may be I overlooked it? I did search for it, can't find it
> in the documenation center.
>
> btw, I did also try the natural language interface also, and I asked
> W/ALpha by typing
>
>      = matrix condition number
>
> but it replied back with a chemical formula C16 H13 C1 N2 O, named diazepam, which is not what I wanted.
>
> thanks,
> --Nasser
>
>

```

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