add a column between tow columns

Hi,

I am newbie with matlab. I have a matrix like:

a = [ 2 5 7 ; 3 6 8]

I would like to add new column between column 1 and 2, So I will have:

a = [2 1 5 7; 3 4 6 8]

Let me ask it more general, I want to add a column between any two columns.

Thanks

Answer 1

[Sara]

Given the array A and the column vector x, let n be the column after which you want to add x into A:

ncol = size(A,2);
cat(2,A(:,1:n),x,A(:,min(n+1,ncol):end))

[Hossein]

would you please tell me the reason of

   min(n+1,ncol)

?

[Sara]

As far as I know, you may add x it at the end of A too, so n+1 would be outside A boundaries. It's just a precaution.

[Hossein]

Clear as crystal now :)

Answer 2

[Hossein]

I found answer my self (actually my friend help me with that. but any other solution is still welcomed :) )

x [1;4];
a = [a(:,1) x a(:,2:end)]

Answer 3

[Adam]

Hi, look here http://www.mathworks.com/matlabcentral/answers/1085-inserting-a-column-in-a-matrix-without-deleting-any-column

If you use it often, some function handling it should not be problem to program.

Adam

Answer 4

[Jos (10584)]

% DATA  
  A = [1 2 3 ; 4 5 6] % original matrix
  x = [8 ; 9] % values to insert
  J = 2 % insert x AFTER column J into A

% ENGINE
  B = [A x] 
  [~,i] = sort([1:size(A,2) J]) 
  B = B(:,i)