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Composing arrayfun syntax to extract data from structure

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Milos on 13 Nov 2012
Here is a simplified example of structure:
C(1,1).idx = [1;1;2;3];
C(2,1).idx = [1;1;2];
C(1,1).s = {'a';'a';'ab';'abc'};
C(2,1).s = {'a';'a';'ab'};
now, find unique idx in structure C:
[ua,ia,~] = arrayfun(@(x) unique(x.idx, 'rows'), C, 'UniformOutput', false);
How do I apply indexes ia to extract corresponding values in s fields? I can think of for loop but is there some arrayfun trick? Side note, in my real data idx is nx4 matrix therefore 'rows' argument.
Milos on 13 Nov 2012
In my example:
ia{1,1} = [2;3;4];
ia{2,1} = [2;3];
Now, how would you, using indexes ia and ARRAYFUN, extract corresponding values from field s?

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Accepted Answer

Matt Fig
Matt Fig on 13 Nov 2012
Edited: Matt Fig on 13 Nov 2012
O.k., if you are just messing around with ARRAYFUN.
C(1,1).idx = [1;1;2;3];
C(2,1).idx = [1;1;2];
C(1,1).s = {'a';'a';'ab';'abc'};
C(2,1).s = {'a';'a';'ab'};
[ua,ia,~] = arrayfun(@(x) unique(x.idx,'rows'),C,'Un',0);
V = arrayfun(@(x) C(x).s(ia{x}),1:length(C),'Un',0)

More Answers (1)

Walter Roberson
Walter Roberson on 13 Nov 2012
arrayfun(@(rowidx,idx) C(rowidx).s(idx{1}), 1:size(C,1), ia, 'UniformOutput', false)
or perhaps this might work:
arrayfun( @(idx, s) s{idx{1}}, ia, {C.s}, 'UniformOutput', false)


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