Matlab: repeat every column sequentially n times [duplicate]

Question

This question already has an answer here:

• Element-wise array replication in Matlab 7 answers

I'm pretty much beginner so it's probably possible to do what I want in a simple way. I have a matrix 121x62 but I need to expand it to 121x1488 so every column has to be repeated 24 times. For example, transform this:

   2.2668       2.2667       2.2667       2.2666       2.2666       2.2666       
   2.2582       2.2582       2.2582       2.2582       2.2581       2.2581       
    2.283        2.283        2.283       2.2829       2.2829       2.2829       
   2.2881       2.2881       2.2881       2.2881       2.2881        2.288        
    2.268        2.268       2.2679       2.2679       2.2678       2.2678       
   2.2742       2.2742       2.2741       2.2741       2.2741        2.274    

into this:

2.2668     2.2668     2.2668  and so on to 24th     2.2667     2.2667  and again to 24x
2.2582     2.2582     2.2582 ...

with every column.

I've tried to create a vector with these values and then transform with vec2mat and ok I have 121x1488 matrix but repeated by rows:

2.2668   2.2668   2.2668  2.2668  2.2668  2.2668 ...    2.2582   2.2582  2.2582  2.2582 ...

How to do it by columns?

Answer 1

Suppose you have this simplified input and you want to expand columns sequentially n times:

A   = [1 4
       2 5
       3 6];

szA = size(A); 
n = 3;

There are few ways to do that:

• Replicate, then reshape:

  reshape(repmat(A,n,1),szA(1),n*szA(2))
  

• Kronecker product:

  kron(A,ones(1,n))
  

• Using FEX: expand():

  expand(A,[1 n])
  

• Since R2015a, repelem():

  repelem(A,1,n)
  

All yield the same result:

ans =
     1     1     1     4     4     4
     2     2     2     5     5     5
     3     3     3     6     6     6

Answer 2

Just for the sake of completeness. If you want to duplicate along the rows, you can also use rectpulse().

A = [1,2,3;...
     4,5,6];

n = 3;

rectpulse(A, n);

gives you

1  2  3
1  2  3
1  2  3
4  5  6
4  5  6
4  5  6

Answer 3

Here You go:

function [result] = repcolumn(A, n)
    %n - how many times each column from A should be repeated

    [rows columns] = size(A);
    result = repmat(A(:,1),1,n);

    for i = 2:columns
        result = [result,repmat(A(:,i),1,n)];
    end
end

There must be an easier way but it does the job.