Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


dpb
Posts:
9,840
Registered:
6/7/07


Re: matrix mean
Posted:
Sep 10, 2013 9:03 AM


On 9/10/2013 4:41 AM, Puneet wrote: > dpb <none@non.net> wrote in message <l0lbpf$lel$1@speranza.aioe.org>... >> On 9/9/2013 6:40 AM, Puneet wrote: >> > Hi  this is begginers question. >> > I have a data set  16 rows and 16 columns  I would like to average >> > every 2 points to get an 8 rows 8 columns matrix. >> > >> > This is a learning phase so I can run something similar later for >> larger >> > data sets. >> > Thanks. >> >> One way...(not necessarily the best :) ) presuming that the "every 2 >> points" means in both directions given the resulting size of output >> for the described input. Similar works w/ filter() for the vector case. >> >> m4=filter2(ones(2)/4,z); >> m4=m4(1:2:end,1:2:end); >> >> Hint: look up 2D convolution... :) >> >> accumarray() could be you friend amongst other ways to attack it...
...
> i would like to rephrase my query. if i have a row vector of length 16 > and i want to average every 2 consecutive elements and save it as a row > vector, then how should i go about it. i know its a beginner query but > may be its too specific as a really couldn't find it any where or even > close to it.
Alternatively to filter()
n=length(z); m2=accumarray([1:n]',[1:2:n]',[],@(i) mean(z(i:i+1)))';




