how to combine matrix easier

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metumetu 2020-3-11

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评论： BobH 2020-3-12

Hello,
I want. How can i do this (below code block) with a loop? 
I have to do this with a loop because, i will be doing this with a lots of a matrices. please help me. 
Thank you.
a1=[1,2,3; 4,5,6; 7,8,9]
a2=[10,11,12; 13,14,15; 16,17,18]
a3=[19,20,21; 22,23,24; 25,26,27]
b1=[a1(:,1);a1(:,2);a1(:,3)] 
b2=[a2(:,1);a2(:,2);a2(:,3)] 
b3=[a3(:,1);a3(:,2);a3(:,3)] 
C=[b1,b2,b3] 

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BobH 2020-3-11

编辑：BobH 2020-3-11

在 MATLAB Online 中打开

You are reading a1/a2/a3 in column order, all rows of col 1, then all rows of col 2, then all rows of col 3. This is the same as the single-index linear indexing

b1 = a1(:)

All the b1/b2/b3 assignments can be eliminated

C = [a1(:) a2(:) a3(:)]

Ameer Hamza 2020-3-11

BobH, the actual problem is that OP wants to do it with lots of matrices, so manually concatenating array will not be practical.

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采纳的回答

Ameer Hamza 2020-3-11

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If the data is stored properly, i.e., in cell array instead of using separate variables, the following one-liner will work

a{1}=[1,2,3; 4,5,6; 7,8,9];
a{2}=[10,11,12; 13,14,15; 16,17,18];
a{3}=[19,20,21; 22,23,24; 25,26,27];
 
C = cell2mat(cellfun(@(x) x(:)', a, 'UniformOutput', 0)')';