Path: news.mathworks.com!newsfeed-00.mathworks.com!kanaga.switch.ch!switch.ch!nrc-news.nrc.ca!newsflash.concordia.ca!canopus.cc.umanitoba.ca!not-for-mail From: Walter Roberson <roberson@hushmail.com> Newsgroups: comp.soft-sys.matlab Subject: Re: Polynomial roots Date: Thu, 29 Apr 2010 16:29:11 -0500 Organization: The University of Manitoba Lines: 18 Message-ID: <hrctn8$7j3$1@canopus.cc.umanitoba.ca> References: <hrcsta$g22$1@fred.mathworks.com> NNTP-Posting-Host: ssh.ibd.nrc.ca Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: canopus.cc.umanitoba.ca 1272576553 7779 132.246.132.10 (29 Apr 2010 21:29:13 GMT) X-Complaints-To: abuse@cc.umanitoba.ca NNTP-Posting-Date: Thu, 29 Apr 2010 21:29:13 +0000 (UTC) User-Agent: Thunderbird 2.0.0.24 (Macintosh/20100228) In-Reply-To: <hrcsta$g22$1@fred.mathworks.com> Xref: news.mathworks.com comp.soft-sys.matlab:631113 Mark wrote: > I'm trying to find the roots of 100 random polynomials of degree 5 and I > need help with finding the roots. I know that I can gernerate 100 > polynomials by using > >> x=rand([100 6]) > I know that I can't do >> roots(x) > because the the input must be a vector. Is there anyway to to find all > the roots of 100 random polynomials without generating each polynomial > one by one. Not for degree 5. For degree 4, there would be exact solutions you could plug the coefficients into, but for degree 5 unless you are lucky enough to be able to factorize, you need to use something like a binary search for sign changes over a hypothesized interval. I'm not saying that it would not be possible to build a routine that did this kind of search in parallel, but it isn't the way the built-in routines are set up.