how to sort the element of one column in a 220*3 matrix in ascending mode, keeping the elements of other columns dependent on the elements of sorted column ?

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Joseph
Joseph 2015-7-20
编辑： Stephen23 2015-7-20
i have a 220*3 matrix. the elements of first column in this matrix is related to the elements of other 2 columns. how can i sort the elements of first column in ascending mode, moving the elements of other columns correlated to the elements of first column?

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Stephen23
Stephen23 2015-7-20
编辑：Stephen23 2015-7-20
If you want to move the entire row based on how the first column is sorted, then use sortrows with its second optional argument (the rows move along with the first column):
sortrows(X,1)
For example:
>> X = [9,1,1,1;1,2,2,2;5,3,3,3]
X =
9 1 1 1
1 2 2 2
5 3 3 3
>> sortrows(X,1)
ans =
1 2 2 2
5 3 3 3
9 1 1 1
If you want to sort only the first column then just use sort and the appropriate indexing (the other columns do not change):
X(:,1) = sort(X(:,1));
  2 个评论
Joseph
Joseph 2015-7-20
and what if a few elements of first column are the same and i decide to sort with the descending elements of third column?
Stephen23
Stephen23 2015-7-20
编辑：Stephen23 2015-7-20
If you had actually read the link to the sortrows documentation that I gave you, then you would already know how: use the second optional argument to do exactly what you want:
sortrows(X,[1,-3])

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更多回答（1 个）

Jan
Jan 2015-7-20
And this happens inside sortrows:
X = rand(220, 3);
[Y, Order] = sort(X(:, 1));
R = X(Order, :);

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