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Select all entries in first N-1 dimensions of array

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Sargondjani
Sargondjani 2012-5-23
hi, i have a loop in which cell array V keeps expanding:
for it=1:10;
V{it}= ..... % the number of dimension of V{it} is 'it'
% so if it=3: size(V{it})=[2 2 2];
end
later im going to loop through V again, but i want to select only the first N dimensions:
for id=1:9;
Y{id}= ... % select first 'id' dimensions of V{id+1}
%so if id=2, W{id}=V{id+1}(:,:,1), but if id=3, W{id}=V{id+1}(:,:,:,1)
end
I just dont know how to adjust the number of ':' i want to be there. Or equivalently to adjust the numer of times to put in 1:2, ie. W{4}=V{5}(1:2,1:2,1:2,1:2,1).
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Sargondjani
Sargondjani 2012-5-23
well, i dont care, i have the answer, hahaha
Oleg wrote something like:
v = [repmat({':'},id-1,1);{1}];
Y{id}=V{id+1}(v{:})

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Daniel Shub
Daniel Shub 2012-5-23
Have you thought about using linear indexing?
V{1} = rand([2,2,2]);
x = reshape(V{1}(1:4), repmat(2, 1, 2));
y = V{1}(1:2, 1:2);
isequal(x,y)
EDIT To give a full working example
Create some data:
for it=1:10;
V{it}= rand([repmat(2, 1, it), 1]);
end
Then get the data you want
for id=1:9;
Y{id} = reshape(V{id+1}(1:(2^(id))), [repmat(2, 1, id), 1]);
end
  2 个评论
Sargondjani
Sargondjani 2012-5-23
the problem is that i dont see how to increase the number of "1:2" after the y=V{1}
but thanks anyway. the problem is solve with the solution that oleg gave...
Sargondjani
Sargondjani 2012-5-23
i see your point after the edit. thanks!! i will need this type of linear indexing later on :-)

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