sorting according to another vector

Asked by Danielle Leblanc on 5 Aug 2011

Latest activity Commented on by Steven Lord on 26 Oct 2018

1.046 views (last 30 days)

Hi,

I have a vector A that doesn't follow any order. I want to sort Matrix B that has the first column of values similar to those of A but in different order. Is it possible to sort B according to A using a single function or should I write many codes to do so?

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4 Answers

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Answer by Walter Roberson on 5 Aug 2011

Accepted Answer

Sorry you will have to use multiple calls:

[a_sorted, a_order] = sort(A);
newB = B(a_order,:);

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Jan on 5 Aug 2011

@Danielle: Ok, then I have misunderstood your question. The information that B has "value similar to those of A" is meaningless then - correct?

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Answer by Jan on 5 Aug 2011

I'm not sure, if I understand the question correctly. Do you want to bring B in the same order as the unsorted A? Then either sort both vectors and mix their sorting indicies:

[As, Ai] = sort(A);
[Bs, Bi] = sort(B(:, 1));
ABi(Ai) = Bi;

Now ABi is the sorting index to bring B to the order of A:

isequal(A, B(ABi, 1)) % ==> 1

Or let ISMEMBER do this for you:

[dummy, order] = ismember(A, B(:, 1));
isequal(A, B(order, 1))  % ==> 1

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Answer by Pramit Biswas on 31 Jan 2018

Edited by Pramit Biswas on 31 Jan 2018

 function B = sortBlikeA(A,B)
   [~, Ao] = sort(A);
   Bs=sort(B);
   B(Ao)=Bs;
 end

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Answer by inzamam shoukat on 26 Oct 2018

Edited by inzamam shoukat on 26 Oct 2018

Hi every one......i have matrix lets suppose [3 2;1 9]

what i want to do is sort out the only first column in ascending order but problem is how to do it so that corresponding values which is in first row 2 for 3 in second row 9 for 1 change their positions according to the position of values of first column being sorted i.e [1 9; 3 2]...

LIMITATION : sorting operation never applied to second column....

2 Comments

madhan ravi on 26 Oct 2018

Please ask a separate question

Steven Lord on 26 Oct 2018

Use sortrows.

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Danielle Leblanc (view profile)