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Anti-diagonal matrix traversal

version (1.43 KB) by Loïc
This function allows you to traverse a square matrix along the anti-diagonal.


Updated 21 May 2010

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This function takes as an input a square matrix and returns two outputs. The first is a vector containing the matrix values starting in the (1,1) entry and progressing along the anti-diagonal elements. A second output gives the sum of the elements along the anti-diagonals.
For example:
a = [1 2 3; 4 5 6; 7 8 9];
[b,c] = diagtrav(a);
b = [1 2 4 3 5 7 6 8 9];
c = [1 6 15 14 9];

Cite As

Loïc (2021). Anti-diagonal matrix traversal (, MATLAB Central File Exchange. Retrieved .

Comments and Ratings (2)


Thank you for your suggestion, this is my first submission. I have updated the file.

Matt Fig

As it is, you have some deficiencies. There is no H1 line. The help is non-standard in its location. There is no input checking: if the function is for square matrices then you should check to see if the input is square. Your algorithm works well, except you cripple the speed by not pre-allocating your return arrays before the loops. Look at the difference:

>> M = round(rand(400)*300);
>> tic,[P,Q]=diagtrav(M);toc % No pre-allocation
Elapsed time is 134.937511 seconds.
>> tic,[P,Q]=diagtrav(M);toc % With pre-allocation
Elapsed time is 0.014006 seconds.

You should pre-allocate the return arrays!

MATLAB Release Compatibility
Created with R2009b
Compatible with any release
Platform Compatibility
Windows macOS Linux

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