CODEWITHSUNDEEP
matlabsorting
well
well

Reputation: 47

Sort rows of a matrix in ascending order

I would like to sort a matrix in ascending order, however I do not want to affect the third column. For example, the sorted version of

A= [ 2 1 3; 
     5 4 1; 
     4 3 2]

Would be

B= [1 2 3; 
    4 5 1; 
    3 4 2]

Upvotes: 0

Views: 349

Answers (2)

matlabgui
matlabgui

Reputation: 5672

You can just sort the 1st two columns and update the matrix accordingly:

edit: updated dimension

A(:,1:2) = sort(A(:,1:2),2);

Upvotes: 1

Carel
Carel

Reputation: 3397

Matlab provides quite a bit of inhouse help so using help FUNCTION/CLASS would have provided you with the below information. If you don't know the FUNCTION\CLASS name use lookfor TERM for a list of matches or alternately docsearch TERM.

Stock matlab provides both sort and sortrows. You'll be needing the latter.

sortrows(X,C)

Where C is a list of column indices to sort by whose sign may be positive corresponding for ascending order or negative for descending order.

In your example you'll want this :

sortrows(A',[1,2])'

The ' indicates to matlab that you need the matrix transposed, which basically swaps rows and columns before and after sortrows is called.

Upvotes: 2

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