Concatenate I x J*2 x K matrix in I*J x 2 x K matrix

1 view (last 30 days)
Hi Guys,
I was using this code line for concatenate a [8 x 4 x 6] matrix in a [16 x 2 x 6] matrix:
X = [x(:,1:2,:); x(:,3:4,:)];
M1 (2).png
Now, I am trying to convert a [200 x 200 x 11] matrix in a [40000 x 2 x 11] matrix, using the code line before mentioned:
X = [x(:,1:2,:); x(:,3:4,:); x(:,5:6,:); x(:,7:8,:); x(:,9:10,:); x(:,11:12,:); x(:,13:14,:); x(:,15:16,:); x(:,17:18,:); x(:,19:20,:); ...
(and so on)
x(:,181:182,:); x(:,183:184,:); x(:,185:186,:); x(:,187:188,:); x(:,189:190,:); x(:,191:192,:); x(:,193:194,:); x(:,195:196,:); x(:,197:198,:); x(:,199:200,:)];
It works, but I can do the same with a for loop (or another approach), and for general matrix array?
[I x J*2 x K] to [I*J x 2 x K]
Thanks for your help in advance.

Accepted Answer

Stephen23
Stephen23 on 3 Dec 2019
Edited: Stephen23 on 3 Dec 2019
Use reshape and permute, e.g. for two columns:
>> A = randi(9,8,4,6); % fake data
>> A(:,:,1)
ans =
9 1 4 6
7 9 7 7
5 6 3 4
6 5 3 5
2 5 3 6
7 2 5 9
1 5 5 2
5 6 4 1
>> B0 = [A(:,1:2,:);A(:,3:4,:)]; % your method for comparison
>> [R,~,P] = size(A);
>> B1 = reshape(permute(reshape(A,R,2,[],P),[1,3,2,4]),[],2,P);
And checking:
>> isequal(B0,B1)
ans = 1
>> B0(:,:,1)
ans =
9 1
7 9
5 6
6 5
2 5
7 2
1 5
5 6
4 6
7 7
3 4
3 5
3 6
5 9
5 2
4 1
>> B1(:,:,1)
ans =
9 1
7 9
5 6
6 5
2 5
7 2
1 5
5 6
4 6
7 7
3 4
3 5
3 6
5 9
5 2
4 1
An example with six columns:
>> A = randi(9,3,6,5); % fake data
>> A(:,:,1)
ans =
2 3 8 8 2 6
5 5 1 5 6 7
2 2 1 8 1 1
>> B0 = [A(:,1:2,:);A(:,3:4,:);A(:,5:6,:)]; % your method for comparison
>> [R,~,P] = size(A);
>> B1 = reshape(permute(reshape(A,R,2,[],P),[1,3,2,4]),[],2,P);
And checking:
>> isequal(B0,B1)
ans = 1
>> B0(:,:,1)
ans =
2 3
5 5
2 2
8 8
1 5
1 8
2 6
6 7
1 1
>> B1(:,:,1)
ans =
2 3
5 5
2 2
8 8
1 5
1 8
2 6
6 7
1 1

More Answers (0)

Categories

Find more on Creating and Concatenating Matrices in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!