Extracting values from a cell array into new arrays

Hi,

I have a 1x44 cell array where each column contains a 72x4 double array. I also have a 10x2 double array. Please see both .mat files attached if further clarification is needed regarding the structure. I am referencing the values in these mat. files in my problem as follows:

I need to extract the double arrays in the 1x44 cell array referenced in the first column of the 10x2 double array into a new cell array. So the first double array extracted for instance would be the 4th column of the cell array.

The second thing I want to do is then extract from the second column of each double array of the new cell array the value referenced in the second column of the 10x2 double array. I would like all rows adjacent to also be extracted. For instance the first values would all be within row 5 of the first double array of the new cell array.

Any suggestions on how to do these two steps would be most welcome.

Answer 1

[Andrei Bobrov]

CC = cat(3,C{:});
[m,n,k] = size(CC);
Z = permute(repmat(b,1,1,n),[1,3,2]);
out = CC(sub2ind([m,n,k],Z(:,:,2),repmat(1:n,size(b,1),1),Z(:,:,1)));

or

n = cellfun('size',C,1);
i = repelem((1:numel(n))',n(:));
CC = cat(1,C{:});
out = CC(ismember([i,CC(:,2)],b,'rows'),:);

in your case

CC = cat(1,C{:});
out = CC(ismember(CC(:,1:2),b,'rows'),:);

Answer 2

[Stephen23]

Step 1: indexing:

D = C(b(:,1));

Step 2: cellfun and an anonymous function:

F = @(m,v)m(m(:,2)==v,:);
Z = cellfun(F,D(:),num2cell(b(:,2)),'uni',0);
W = cell2mat(Z) % optional

Giving:

W =
            4            5       2.4181      0.43232
            8           63       2.7632      0.44257
           12           45       3.7255      0.41266
           20            3       5.3249      0.11164
           24           22       1.4465      0.30058
           28           18       3.1631      0.58063
           31           71       2.0108       0.2431
           33           66       1.0293      0.38437
           36           50       1.7156      0.36392
           43            2       2.0634      0.14015

Checking the first row by hand:

>> b(1,1)
ans =
     4
>> T = C{4};
>> T(T(:,2)==b(1,2),:)
ans =
            4            5       2.4181      0.43232