Dynamic Matrices in Matlab
3 views (last 30 days)
Show older comments
Hi!
Yesterday, I had a very similar question, now I want something a bit more advanced. So I have coded already:
data = [234,3,8;457,5,7;611,7,3;234,9,12]
ID = data(:,1);
X = data(:,2);
U = unique(ID)
data(U(i) == data(:,1),3)
display data
Now I want to create a matrix, where the first column would be the first column of the data matrix above (i.e. "id"). And all the following collumns would then store the values in the third column of data belonging to this id. So it would look like:
[234, 8,12; 457, 7,0; --- ]
But, obviously, I could not set the dimensions of this matrix from the beginning on, the number of columns would have to be dynamical. Is that possible?
Thanks
2 Comments
Answers (2)
Andrei Bobrov
on 13 Dec 2012
Edited: Andrei Bobrov
on 13 Dec 2012
[a,b,c] = unique(data(:,1));
d = accumarray(c,data(:,3),[],@(x){sort(x)});
n = cellfun(@numel,d);
m = numel(a);
out = [a, zeros(m,max(n))];
for j1 = 1:m
out(j1,2:n(j1)+1) = d{j1};
end
2 Comments
Walter Roberson
on 13 Dec 2012
Is the number of matching elements possibly different between the id's? If it is, then you cannot do this with a numeric matrix and need to use a cell array instead.
0 Comments
See Also
Categories
Find more on Structures in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!