Thread Subject: Sort columns of numbers

Hello,

This is undoubtably a simple question but it is a puzzling me. I have the following:

4 9
3 8
5 12
6 13
1 4
2 19

How can i sort the matrix so it reads:
1 4
2 19
3 8
4 9
5 12
6 13

i.e. how can i sort column 1 so that it is ascending but also move the corresponding value in column 2 to the correct position?

Any help would be great.

Thanks in advance,

Phil

"Phil " <harsh_classic@yahoo.co.uk> wrote in message <h7isn2$30i$1@fred.mathworks.com>...
> Hello,
>
> This is undoubtably a simple question but it is a puzzling me. I have the following:
>
> 4 9
> 3 8
> 5 12
> 6 13
> 1 4
> 2 19
>
> How can i sort the matrix so it reads:
> 1 4
> 2 19
> 3 8
> 4 9
> 5 12
> 6 13
>
> i.e. how can i sort column 1 so that it is ascending but also move the corresponding value in column 2 to the correct position?
>
> Any help would be great.
>
> Thanks in advance,
>
> Phil

a hint:

     help sortrows;

us

"Phil " <harsh_classic@yahoo.co.uk> wrote in message
news:h7isn2$30i$1@fred.mathworks.com...
> Hello,
>
> This is undoubtably a simple question but it is a puzzling me. I have the
> following:
>
> 4 9
> 3 8
> 5 12
> 6 13
> 1 4
> 2 19
>
> How can i sort the matrix so it reads:
> 1 4
> 2 19
> 3 8
> 4 9
> 5 12
> 6 13
>
> i.e. how can i sort column 1 so that it is ascending but also move the
> corresponding value in column 2 to the correct position?
>
> Any help would be great.
>
> Thanks in advance,
>
> Phil

EDU>> A=[4 9;
3 8;
5 12;
6 13;
1 4;
2 19];

sortrows(A)

ans =

     1 4
     2 19
     3 8
     4 9
     5 12
     6 13

--Nasser

"Phil " <harsh_classic@yahoo.co.uk> wrote in message <h7isn2$30i$1@fred.mathworks.com>...
> Hello,
>
> This is undoubtably a simple question but it is a puzzling me. I have the following:
>
> 4 9
> 3 8
> 5 12
> 6 13
> 1 4
> 2 19
>
> How can i sort the matrix so it reads:
> 1 4
> 2 19
> 3 8
> 4 9
> 5 12
> 6 13
>
> i.e. how can i sort column 1 so that it is ascending but also move the corresponding value in column 2 to the correct position?
>
> Any help would be great.
>
> Thanks in advance,
>
> Phil

doc sortrows

Thanks to all!

"Aurelien Queffurust" <tug83@yahoo.fr> wrote in message <h7it5s$6l5$1@fred.mathworks.com>...
> "Phil " <harsh_classic@yahoo.co.uk> wrote in message <h7isn2$30i$1@fred.mathworks.com>...
> > Hello,
> >
> > This is undoubtably a simple question but it is a puzzling me. I have the following:
> >
> > 4 9
> > 3 8
> > 5 12
> > 6 13
> > 1 4
> > 2 19
> >
> > How can i sort the matrix so it reads:
> > 1 4
> > 2 19
> > 3 8
> > 4 9
> > 5 12
> > 6 13
> >
> > i.e. how can i sort column 1 so that it is ascending but also move the corresponding value in column 2 to the correct position?
> >
> > Any help would be great.
> >
> > Thanks in advance,
> >
> > Phil
>
> doc sortrows

Dear Phil!

> 4 9
> 3 8
> 5 12
> 6 13
> 1 4
> 2 19
>
> How can i sort the matrix so it reads:
> 1 4
> 2 19
> 3 8
> 4 9
> 5 12
> 6 13
>
> i.e. how can i sort column 1 so that it is ascending but also move the corresponding value in column 2 to the correct position?

The already mentioned SORTROWS cares for the 2nd column also. If this is not wanted, you can sort the first column and apply the index to the 2nd column:
  A = [4, 9; ...
         3, 8; ...
         5, 12; ...
         6, 13; ...
         1, 4; ...
         2, 19];
  [A1, SortIndex] = sort(A(:, 1));
  ASorted = A(SortIndex, :);
or
  ASorted = [A1, A(SortIndex, 2)]; % slower

Th result differs from SORTROWS, if the numbers in the first column are not unique.

Kind regards, Jan