Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: matlab alternative to mtimesx for this problem ? Date: Sun, 28 Aug 2011 23:24:09 +0000 (UTC) Organization: University of Waterloo Lines: 31 Message-ID: <j3eimp$op4$1@newscl01ah.mathworks.com> References: <j3e342$dbb$1@newscl01ah.mathworks.com> <j3eb5j$52j$1@newscl01ah.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: www-04-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: newscl01ah.mathworks.com 1314573849 25380 172.30.248.35 (28 Aug 2011 23:24:09 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Sun, 28 Aug 2011 23:24:09 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 1646679 Xref: news.mathworks.com comp.soft-sys.matlab:741518 Merci Bruno, "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message > > I want to integrate a function of w and t, wrt w, so the final answer should be a function of t. > Wait a minute, why you need to do thing so inefficiently? Sometime you just have to think harder than what you really computes. > > The above results are equal to (at numerical precision) > > > d = trapz(w,w)*t(:); This is obviously not true for all functions of w and t, and the example I gave wasn't actually the function I'm integrating, but a simpler example. > BTW: > repmat(w,length(t),1).*repmat(t',1,length(w)), > bsxfun(@times,w,t') > mtimesx(w,'T',t) > > is simply: > > > t'*w > Thank you. But: tic;d=trapz(w,t'*w,2);toc takes 4GB of RAM and 52 seconds. (same as REPMAT and BSXFUN)