add a column between tow columns

2014 5 29
4 个回答
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更新时间：2014 5 29
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0 个投票

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

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Sara
Sara 2014-5-29

2 个投票

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))

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Hossein
Hossein 2014-5-29
would you please tell me the reason of
min(n+1,ncol)
?
Sara
Sara 2014-5-29
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
Hossein 2014-5-29
Clear as crystal now :)

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更多回答（3 个）

Hossein
Hossein 2014-5-29
编辑：Hossein 2014-5-29

1 个投票

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)]
Jos (10584)
Jos (10584) 2014-5-29

0 个投票

% 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)

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