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From: Ioannis Mitsos on 18 Jan 2010 07:21
Hello,

Lets say that I have the matrix:

NN=[ 1 2 3
4 1 9
3 5 9
2 9 3]

which are coordinates on a 3d system. What I want to do is to sort them in an ascending order according to the value of the elements of the first column. So the result will be:

NN=[1 2 3
2 9 3
3 5 9
4 1 9];

Does anybody have an idea how to do it?

From: Jan Simon on 18 Jan 2010 07:35
Dear Ioannis!

> NN=[ 1 2 3
> 4 1 9
> 3 5 9
> 2 9 3]
>
> which are coordinates on a 3d system. What I want to do is to sort them in an ascending order according to the value of the elements of the first column. So the result will be:
>
> NN=[1 2 3
> 2 9 3
> 3 5 9
> 4 1 9];

[dummy, SortIndex] = sort(NN(:, 1));
NNsorted = NN(SortIndex, :)

Good luck, Jan
From: Jos (10584) on 18 Jan 2010 07:53
"Ioannis Mitsos" <ioannis-mitsos(a)hotmail.com> wrote in message <hj1jnf$cdu$1(a)fred.mathworks.com>...
> Hello,
>
> Lets say that I have the matrix:
>
> NN=[ 1 2 3
> 4 1 9
> 3 5 9
> 2 9 3]
>
> which are coordinates on a 3d system. What I want to do is to sort them in an ascending order according to the value of the elements of the first column. So the result will be:
>
> NN=[1 2 3
> 2 9 3
> 3 5 9
> 4 1 9];
>
> Does anybody have an idea how to do it?
>

help sortrows

Jos
From: Ioannis Mitsos on 18 Jan 2010 08:05
"Jan Simon" <matlab.THIS_YEAR(a)nMINUSsimon.de> wrote in message <hj1khp$4p9$1(a)fred.mathworks.com>...
> Dear Ioannis!
>
> > NN=[ 1 2 3
> > 4 1 9
> > 3 5 9
> > 2 9 3]
> >
> > which are coordinates on a 3d system. What I want to do is to sort them in an ascending order according to the value of the elements of the first column. So the result will be:
> >
> > NN=[1 2 3
> > 2 9 3
> > 3 5 9
> > 4 1 9];
>
> [dummy, SortIndex] = sort(NN(:, 1));
> NNsorted = NN(SortIndex, :)
>
> Good luck, Jan


Jan it works perfectly!!I really appreciate your help!!Thanks a lot ;-)
cheers,
Ioannis
From: Jan Simon on 18 Jan 2010 12:31
Dear Jos!

> > NN=[ 1 2 3
> > 4 1 9
> > 3 5 9
> > 2 9 3]
> >
> > NN=[1 2 3
> > 2 9 3
> > 3 5 9
> > 4 1 9];
>
> help sortrows

The given example does not distinguish between SORTROWS or SORT of first line. The OP has to define what should happen for:
NN=[ 1 2 3
4 2 9
4 1 9
3 5 9
2 9 3]
What is the last row then?
SORTROWS: [4 2 9], because it is "greater" than [4 1 9]
SORT(1st column): [4 1 9], because it is "later" in the input.

Kind regards, Jan
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