# Compact way to horizontally concatenate a cell array without the first columns of the cells

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Sim on 7 Apr 2022
Commented: Sim on 7 Apr 2022
Hi, I have two matrices A and B that are "stored" inside a cell array C.
Just manipulating the cell array C (and not matrices A and B), I would like to horizontally concatenate the two cells of C in a compact way, with the condition of not taking the first column of both cells.
Here my example:
% input
A = [2 4 6
1 3 8
6 9 1
6 1 1
5 5 2
3 7 8
9 2 4]
B = [8 3 5
9 9 5
6 3 1
7 1 2
4 8 7
2 2 4
5 7 3]
% creation of the cell array C
C{1} = A;
C{2} = B;
% horizontal concatenation of the C's cells
D = horzcat(C{:})
% result - just using horzcat(C{:}), the first columns of A and B are present
D =
2 4 6 8 3 5
1 3 8 9 9 5
6 9 1 6 3 1
6 1 1 7 1 2
5 5 2 4 8 7
3 7 8 2 2 4
9 2 4 5 7 3
% desired output - where the first columns of A and B are absent
D =
4 6 3 5
3 8 9 5
9 1 3 1
1 1 1 2
5 2 8 7
7 8 2 4
2 4 7 3
% Note: the following naive attempt gives me an error
>> horzcat(C{:}(:,2:3))
Expected one output from a curly brace or dot indexing expression, but there were 2 results.
Is there any compact way to get my desired output,
• just manipulating C (and not A and B) and
• possibly still using horzcat (or similar built-in functions), like/similarly to horzcat(C{:}) ?

Stephen23 on 7 Apr 2022
Edited: Stephen23 on 7 Apr 2022
It rather depends on what you mean by "compact".
C = {[2,4,6;1,3,8;6,9,1;6,1,1;5,5,2;3,7,8;9,2,4],[8,3,5;9,9,5;6,3,1;7,1,2;4,8,7;2,2,4;5,7,3]}
C = 1×2 cell array
{7×3 double} {7×3 double}
Method one, probably simplest and clearest:
D = horzcat(C{:});
D(:,1:3:end) = []
D = 7×4
4 6 3 5 3 8 9 5 9 1 3 1 1 1 1 2 5 2 8 7 7 8 2 4 2 4 7 3
Method two: CELLFUN and CELL2MAT:
D = cell2mat(cellfun(@(m)m(:,2:end),C,'uni',0))
D = 7×4
4 6 3 5 3 8 9 5 9 1 3 1 1 1 1 2 5 2 8 7 7 8 2 4 2 4 7 3
Method three: CELLFUN and HORZCAT (probably more efficient than CELL2MAT):
D = cellfun(@(m)m(:,2:end),C,'uni',0);
D = horzcat(D{:})
D = 7×4
4 6 3 5 3 8 9 5 9 1 3 1 1 1 1 2 5 2 8 7 7 8 2 4 2 4 7 3
Sim on 7 Apr 2022
Cool!! thanks a lot @Stephen!!
Works perfectly for several (and larger) matrices!
% input
A = [2 4 6 1
1 3 8 3
6 9 1 5
6 1 1 6
5 5 2 2
3 7 8 1
9 2 4 6];
B = [8 3 5 1
9 9 5 2
6 3 1 8
7 1 2 9
4 8 7 9
2 2 4 6
5 7 3 7];
W = [5 6 8 5
3 4 7 1
6 3 1 8
9 7 3 9
2 2 3 1
3 8 9 1
5 5 8 2];
Z = [6 4 2 3
1 1 1 9
9 8 9 4
2 1 4 5
9 3 1 2
8 7 7 9
6 5 3 7];
% creation of the cell array C
C{1} = A;
C{2} = B;
C{3} = W;
C{4} = Z;
% horizontally concatenation of the C's cells
D = cellfun(@(m)m(:,2:end),C,'uni',0);
D = horzcat(D{:})
% result with Method three
D =
4 6 1 3 5 1 6 8 5 4 2 3
3 8 3 9 5 2 4 7 1 1 1 9
9 1 5 3 1 8 3 1 8 8 9 4
1 1 6 1 2 9 7 3 9 1 4 5
5 2 2 8 7 9 2 3 1 3 1 2
7 8 1 2 4 6 8 9 1 7 7 9
2 4 6 7 3 7 5 8 2 5 3 7