How to I combine different numbers of columns from two matrices?

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I have two matrices, A and B, and would like to generate a third matrix, C, that contains column 1 of A followed by columns 1:3 of B, then column 2 of A followed by columns 4:6 of B, and so on, until the end of matrix A is reached. I know I can individually generate each group of [A(:,x),B(:,x:x+2)] and then concatenate them, but I'd like to make one loop function to read matrices of any size.

Respuesta aceptada

Mohammad Abouali
Mohammad Abouali el 23 de Oct. de 2015
Editada: Mohammad Abouali el 23 de Oct. de 2015
No loop is needed. Check this:
% Sample A and B
A=repmat(1:4,3,1); % A has its column filled with number 1 to 4
A =
1 2 3 4
1 2 3 4
1 2 3 4
B=repmat(5:16,3,1); % B has its column filled with number 5 to 16
B =
5 6 7 8 9 10 11 12 13 14 15 16
5 6 7 8 9 10 11 12 13 14 15 16
5 6 7 8 9 10 11 12 13 14 15 16
nColA=size(A,2);
if (size(B,2)<(nColA*3))
error('B does not have enough column');
end
if (size(B,1)~=size(A,1))
error('A and B must have same number of rows');
end
% Initializing C
C=NaN(size(A,1),nColA*4);
% PLacing A in C
C(:,((1:nColA)-1)*4+1)=A;
% Placeing B in C
C(:,(1:nColA*3)+floor(((1:nColA*3)-1)/3)+1)=B;
C =
1 5 6 7 2 8 9 10 3 11 12 13 4 14 15 16
1 5 6 7 2 8 9 10 3 11 12 13 4 14 15 16
1 5 6 7 2 8 9 10 3 11 12 13 4 14 15 16

Más respuestas (1)

Guillaume
Guillaume el 26 de Oct. de 2015
I would have done it with a logical array:
A=repmat(1:4,3,1); % A has its column filled with number 1 to 4
B=repmat(5:16,3,1); % B has its column filled with number 5 to 16
filler = repmat(logical([1 0 0 0]), size(A)); %logical array. 1 indicates use A, 0 indicates use B.
C = zeros(size(filler)); %output array
C(filler) = A; %fill 1 with A
C(~filler) = B %fill 0 with B
Simpler than calculating column indices.

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