Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: obatining mean value for every fixed numbers of elements Date: Mon, 15 Dec 2008 06:26:01 +0000 (UTC) Organization: The MathWorks, Inc. Lines: 26 Message-ID: <gi4t9p$dm9$1@fred.mathworks.com> References: <gi2ksb$qsa$1@fred.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: webapp-05-blr.mathworks.com Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8bit X-Trace: fred.mathworks.com 1229322361 14025 172.30.248.35 (15 Dec 2008 06:26:01 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Mon, 15 Dec 2008 06:26:01 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 1187260 Xref: news.mathworks.com comp.soft-sys.matlab:506991 "Yihui Hung" <a489930026@yahoo.com.tw> wrote in message <gi2ksb$qsa$1@fred.mathworks.com>... > Hello, > I have a 6X4 data set and need to average them across every 3X2 data point. The example is as follows: > 1, 2,3,4; > 3, 4, 5,6; > 7, 8, 9,10; > 11, 12, 13, 14; > 15, 16,17,18; > 19,20,21 22; > I would like to obtain four means from1,3,7,2,4,8;3,5,9,4,6,10;11,15,19,12,16,20;13,17,21,14,18,22. Are there some useful matlab function to do this? Any suggestion will appreciated. > > Sincerely, > Yihui Let A be your matrix and let the means be taken over p x q submatrices. Then execute the following (mysterious) code: [M,N] = size(A); m = M/p; n = N/q; % <-- m and n must evaluate to integers [J,I] = meshgrid(p*(0:m*n-1)+m*p*(q-1)*floor((0:m*n-1)/m),... (1:p*q)+(m-1)*p*floor((0:p*q-1)/p)); B = reshape(mean(reshape(A(I+J),p*q,m*n)),m,n); Matrix B will be the requested m x n matrix of mean values. Roger Stafford