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## Re: what does 'mpoles' function do ? (what is 'poles' in it ?)

 From: Ben Abbott Subject: Re: what does 'mpoles' function do ? (what is 'poles' in it ?) Date: Sat, 25 Jun 2011 18:55:13 -0400

```On Jun 25, 2011, at 5:13 PM, Sergei Steshenko wrote:

> Hello,
>
> 'mpoles' function (http://octave.sourceforge.net/octave/function/mpoles.html)
> can be found under "Finding Roots" - see
> http://octave.sourceforge.net/octave/overview.html .
>
> So, because of the "Finding Roots" I _guess_ the function deals with _roots_.
>
> However, the description talks about poles.
>
> I studied math and calculus quite a time ago, so I could easily forget what
> it's all about. AFAIR, if we have a
>
> numerator / denominator
>
> expression, and both numerator and denominator are polynomials, then
> roots of numerator are called zeros and roots of denominator are called
> poles. But both zeros and poles are related to the whole expression.
>
> But other than that I do not know what poles have to do with polynomials.
>
> Could anybody please clarify regarding 'mpoles' and poles it deals with ?
>
> Thanks,
>  Sergei.

You're inference is correct.

mpoles() is used by the residue() function to identify a multiplicity of poles
for A(z)/B(z).

Ben

```