Path: news.mathworks.com!not-for-mail From: "Loren_Shure" <loren.shure@mathworks.com> Newsgroups: comp.soft-sys.matlab Subject: Re: Angle between two vectors Date: Mon, 19 Jul 2010 08:21:39 -0400 Organization: MathWorks Lines: 31 Message-ID: <i21g0k$ker$1@fred.mathworks.com> References: <ef5ce9c.-1@webcrossing.raydaftYaTP> <fjj9nj$fia$1@fred.mathworks.com> <fjk0tg$jli$1@fred.mathworks.com> <fl377q$4ip$1@fred.mathworks.com> <fl3moi$pvc$1@fred.mathworks.com> <i1su0s$deu$1@fred.mathworks.com> <i1t7en$gvq$1@fred.mathworks.com> <i1umi8$r2p$1@fred.mathworks.com> <i1v3gj$8rh$1@fred.mathworks.com> <i1vcn1$s7p$1@fred.mathworks.com> <i1vhmb$1rq$1@fred.mathworks.com> <i1vm13$ok8$1@fred.mathworks.com> NNTP-Posting-Host: ah-loren0w.dhcp.mathworks.com Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=response Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1279542100 20955 172.31.57.72 (19 Jul 2010 12:21:40 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Mon, 19 Jul 2010 12:21:40 +0000 (UTC) In-Reply-To: <i1vm13$ok8$1@fred.mathworks.com> X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Newsreader: Microsoft Windows Live Mail 14.0.8089.726 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8089.726 Xref: news.mathworks.com comp.soft-sys.matlab:654142 "Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in message news:i1vm13$ok8$1@fred.mathworks.com... > "Bard R." <this.is.not.a.real.address@gmail.com> wrote in message > <i1vhmb$1rq$1@fred.mathworks.com>... >> This is exactly what I was looking for. And so much more compact than the >> solution I had put together during the day. It works if A and B are >> opposite (I had to do an extra check for that as well) and for my >> application N is by definition never parallell to neither A nor B. >> Thanx a lot! >> Bě±…rd > - - - - - - - - - - - - > Well, if A and B, or even their projections, are in opposite directions, > the outcome can suddenly flip from one extreme to the other depending on > rounding. A roundoff one way gets +pi as a result and in the other > direction flips the answer over to -pi. I don't see any good way out of > that problem. It is more or less inherent in the nature of numerical > computation of angles. A digital computer cannot even compute the exact > value of pi itself. > > Roger Stafford Have you checked out the function subspace: http://www.mathworks.com/access/helpdesk/help/techdoc/ref/subspace.html ? -- Loren http://blogs.mathworks.com/loren/ http://matlabwiki.mathworks.com/MATLAB_FAQ