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## RE: calculating the eigen matrix

 From: Tapesh Subject: RE: calculating the eigen matrix Date: Fri, 4 Jun 2004 12:48:11 -0500

```Hi Quentin,

It is working perfectly fine..

Could you please also help me in one other problem? I have C style
<double> array and I want to create Matrix out of it. I didn't find any
constructor which take the double[] and create matrix.

Currently I am doing like this: (using the fill() function)
Matrix a(3,3);
//a = [ 1, 1, 2; 3, 5, 8; 13, 21, 34 ];
a.fill(1,0,0,0,0);
a.fill(1,0,1,0,1);
a.fill(2,0,2,0,2);

a.fill(3,1,0,1,0);
a.fill(5,1,1,1,1);
a.fill(8,1,2,1,2);

a.fill(13,2,0,2,0);
a.fill(21,2,1,2,1);
a.fill(34,2,2,2,2);

Is this the right way? I am not confident if it is the efficient way to
do it.

Tapesh

-----Original Message-----
Sent: Friday, June 04, 2004 9:20 PM
Subject: Re: calculating the eigen matrix

This is from some old code I wrote:

ComplexMatrix R(size,size), V(size,size);
// Assign R to something...
V = EIG(R).eigenvectors();

Note that the data type doesn't have to be ComplexMatrix--it could also
be just Matrix. I only needed the eigenvectors in this particular
application. If you wanted both eigenvalues and eigenvectors, a better
way would probably be something like this:

EIG EVD;
Matrix A,B;
ColumnVector c;
// Assign A to something...
EVD=EIG(A);
B=EVD.eigenvectors();
c=EVD.eigenvalues();

This code is untested--just based on what I remember from doing this
sort of thing in the past. I hope this helps.

Regards,
Quentin Spencer

Tapesh wrote:

> Hi,
>
>
>
> I am writing an application in C/C++ and want to use Octave library to

> calculate the eigen matrix and eigen-values.
>
>
>
> I am able to compile octave successfully and to write a sample C++
> programme.
>
>
>
> Can someone provide a sample code to calculate eigen vectors?
>
>
>
>
>
>
> Tapesh Kr. Agarwal
>
>
>

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