# Root finding procedure? Classic List Threaded 4 messages Open this post in threaded view
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## Root finding procedure?

 I am looking for octave- or matlab-code, that allows me to find the roots of the polynomial of x that results from det(H)=0, where the Hij are polynomials in x theirself. E.g.: find the roots x for        3x-4    2x+9 det (                 ) = 0        -x+22   4x-11 I can program such a procedure myself (with successive convolution), but this problem seems standard enough to me, that there could be a procedure out there in octave-land. Any hints? Thomas Hoffmann.
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## Re: Root finding procedure?

 The thing that comes to mind is fsolve.  Write a m-file which takes x as an argument and return det(H).  Use fsolve and it will return the value of x that makes det(H) as close to zero as possible.  Of course there will be a problem with multiple roots and so the answer you get will depend on the starting value you give to fsolve.  I don't know of one that returns all the roots. On Fri, 4 Jul 1997, Thomas Hoffmann wrote: > I am looking for octave- or matlab-code, that allows me to find the > roots of the polynomial of x that results from det(H)=0, where the Hij > are polynomials in x theirself. > E.g.: find the roots x for > >        3x-4    2x+9 > det (                 ) = 0 >        -x+22   4x-11 > > I can program such a procedure myself (with successive convolution), > but this problem seems standard enough to me, that there could be a > procedure out there in octave-land. > Any hints? > > Thomas Hoffmann. >