Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: Angle between two vectors Date: Mon, 19 Jul 2010 12:38:04 +0000 (UTC) Organization: UniversitätsSpital Zürich Lines: 37 Message-ID: <i21gvc$kls$1@fred.mathworks.com> References: <ef5ce9c.-1@webcrossing.raydaftYaTP> <fjj9nj$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$1@fred.mathworks.com> <i21g0k$ker$1@fred.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: webapp-03-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1279543084 21180 172.30.248.38 (19 Jul 2010 12:38:04 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Mon, 19 Jul 2010 12:38:04 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 11 Xref: news.mathworks.com comp.soft-sys.matlab:654149 "Loren_Shure" <loren.shure@mathworks.com> wrote in message <i21g0k$ker$1@fred.mathworks.com>... > > "Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in > message news:i1vm13$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! > >> B책rd > > - - - - - - - - - - - - > > 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 dearest loren if you carefully wade through this thread you'll find out that it has been discussed at length, already... :-) urs