How to average certain elements in a matrix using for loop.
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Hello,
I am trying to operate on a matrix that has the following columns:
M=[x_coordinates y_coordinates ID] I would like to find the average x and y coordinates for same ID, in other words to group all the points that has the same ID. Can you please advice me on how to do it with Matlab.
Best regards, Jack
采纳的回答
Azzi Abdelmalek
2014-3-3
A=[ 1 2 10;5 8 10;4 3 20]
c1=A(:,1);
c2=A(:,2);
[ii,jj,kk]=unique(A(:,3));
cc1=[ii accumarray(kk,c1,[],@mean)]
cc2=[ii accumarray(kk,c2,[],@mean)]
2 个评论
jack
2014-3-3
Azzi Abdelmalek
2014-3-3
A=[ 1 2 10;5 8 10;4 3 20]
weight=[10;54;87]
c1=A(:,1);
[ii,jj,kk]=unique(A(:,3));
cc1=[ii accumarray(kk,c1.*weight,[],@mean)]
更多回答（2 个）
Sean de Wolski
2014-3-3
doc accumarray
And an example:
%%sample data
n = 50;
id = randi(5,n,1);
x = rand(n,1);
y = rand(n,1);
%%engine
[uid,~,idx] = unique(id); % unique ids and the index of occurrences
mx = accumarray(id,x,[],@mean); % mean of x by id
my = accumarray(id,y,[],@mean); % mean of y by id
results = [uid mx my] % display
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