how to reorder the elements of a matrix

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Alina
Alina on 29 Mar 2014
Edited: Sagar Damle on 31 Mar 2014
A=[1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16]
i want to reorder the elements of A into
A=[16 15 12 8
11 14 13 10
7 4 3 6
9 5 2 1 ]
  6 Comments
Roger Stafford
Roger Stafford on 30 Mar 2014
What would your pattern be if A were 5x5, 6x6, or nxn? Are you interested in generalizing in that manner?

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Answers (2)

Star Strider
Star Strider on 29 Mar 2014
Edited: Star Strider on 29 Mar 2014
Here’s one solution. I have no idea if it can be generalised to other matrices.
B = flipud(A)
dl = size(A,1);
C = [];
for k1 = sum(size(A))-1 : -1 : 1
dg = diag(B,k1-dl)
if mod(k1,2) == 1
dg = flipud(dg)
end
C = [C; dg]
end
D = reshape(C,size(A))'

Roger Stafford
Roger Stafford on 29 Mar 2014
Here's a one-liner, though it doesn't exhibit the ingenuity that Star's does.
A = A([16,12,15,14;11,8,4,7;10,13,9,6;3,2,5,1]);
Like Star, I have no idea how this is supposed to generalize. I think you will have to give many more examples or else a more thorough explanation than "zig-zag" if the logic behind this request is to be understood, Alina.
  2 Comments
Image Analyst
Image Analyst on 30 Mar 2014
Edited: Image Analyst on 30 Mar 2014
Nice and simple. She did not ask for it to be generalized. Hence, this is what she gets as the most direct answer. If she comes back and says "how can I generalize?" then you can say "Well, why didn't you say so in the beginning!?!?"
Sagar Damle
Sagar Damle on 30 Mar 2014
Edited: Sagar Damle on 31 Mar 2014
I think to generalize the answer for this question,one can work on code for function 'pascal()' available in MATLAB.I have not got the logic in that code uptil now,but though I think that the code will help in zig-zag coding.

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