Composing arrayfun syntax to extract data from structure

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.

[Azzi Abdelmalek]

It's not clear for me

[Matt Fig]

You realize that ARRAYFUN is almost always slower than a FOR loop, right? I just want to make sure you are not going this route to gain speed...

[Sean de Wolski]

+1 to Matt Fig's comment.

[Milos]

@Matt & @ Sean

I realize ARRAYFUN is slower in many cases, just trying to warp my head around ARRAYFUN and its use.

[Milos]

@Azzi

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?

Answer 1

[Matt Fig]

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)

Answer 2

[Walter Roberson]

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)