CODEWITHSUNDEEP
matlabsorting
belgarion
belgarion

Reputation: 115

How to sort an array while keeping the order of the index row matching the sorted row?

Easiest way is to show you through excel:

Unsorted:

Need to sort second column while keeping the first one matching

Sorted:

Second column sorted, first column follows second column

This example is with excel, but I would need to do the same thing in matlab with thousands of entries (with 2 rows if possible).

Here is my code so far:

%At are random numbers between 0 and 2, 6000 entries.

    [sorted]=sort(At);
    max=sorted(end);
    min=sorted(1);
%need the position of the min and max

But this is only 1 row that's being sorted and it has no numbers in the second row, and no index. How would I add one and keep it following my first row?

Thank you!

Upvotes: 0

Views: 173

Answers (2)

Phillip Ngan
Phillip Ngan

Reputation: 16126

I don't have access to Matlab, but try

[sorted, I] = sort(At);

Where I will be a corresponding vector of indices of At. See the Matlab Documentation for details.

Upvotes: 2

Mad Physicist
Mad Physicist

Reputation: 114538

You have a couple of options here. For the simple case where you just need the indices, the fourth form of sort listed in the docs already does this for you:

[sorted, indices] = sort(At);

In this case, At(indices) is the same as sorted.

If your "indices" are actually another distinct array, you can use sortrows:

toSort = [At(:) some_other_array(:)];
sorted = sortrows(toSort);

In this case sorted(:, 1) will be the sorted array from the first example and sorted(:, 2) will be the other array sorted according to At.

sortrows accepts a second parameter which tells you the column to sort by. This can be a single column or a list of columns, like in Excel. It can also provide a second output argument, the indices, just like regular sort.

Upvotes: 1

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