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From: Faisal Ahmed on 26 Jul 2010 07:56
Suppose I have the following array

1.0000 2.0000 0.4231
1.0000 3.0000 0.8050
1.0000 4.0000 0.7116
2.0000 4.0000 0.6682
2.0000 5.0000 0.4460
2.0000 7.0000 0.5818
3.0000 4.0000 0.0977
3.0000 6.0000 0.5989
3.0000 7.0000 0.3237
4.0000 7.0000 0.2882
5.0000 6.0000 0.1456
5.0000 7.0000 0.3168
6.0000 7.0000 0.2767

I want to sort rows according to the elements of column 3 in a descending order.
So that the sorted array is like:
1.0000 3.0000 0.8050
1.0000 4.0000 0.7116
2.0000 4.0000 0.6682
3.0000 6.0000 0.5989
.......................................
.......................................

Note that, if I use 'sortrows' then the array is sorted in a ascending order automatically which I could not change. If I use 'sort', each column is sorted individually which is not what I want. Any help would be highly appreciated.

-Faisal
From: us on 26 Jul 2010 08:06
"Faisal Ahmed"
> Note that, if I use 'sortrows' then the array is sorted in a ascending order automatically which I could not change. If I use 'sort', each column is sorted individually which is not what I want. Any help would be highly appreciated.
>
> -Faisal

well...
carefully peruse

doc sortrows;
% in particular, look at the second input args...
% eg, what happens if you change the sign of one of them(?)...

us
From: Wayne King on 26 Jul 2010 08:10
"Faisal Ahmed" <fap87(a)yahoo.com> wrote in message <i2jt4m$6aa$1(a)fred.mathworks.com>...
> Suppose I have the following array
>
> 1.0000 2.0000 0.4231
> 1.0000 3.0000 0.8050
> 1.0000 4.0000 0.7116
> 2.0000 4.0000 0.6682
> 2.0000 5.0000 0.4460
> 2.0000 7.0000 0.5818
> 3.0000 4.0000 0.0977
> 3.0000 6.0000 0.5989
> 3.0000 7.0000 0.3237
> 4.0000 7.0000 0.2882
> 5.0000 6.0000 0.1456
> 5.0000 7.0000 0.3168
> 6.0000 7.0000 0.2767
>
> I want to sort rows according to the elements of column 3 in a descending order.
> So that the sorted array is like:
> 1.0000 3.0000 0.8050
> 1.0000 4.0000 0.7116
> 2.0000 4.0000 0.6682
> 3.0000 6.0000 0.5989
> .......................................
> .......................................
>
> Note that, if I use 'sortrows' then the array is sorted in a ascending order automatically which I could not change. If I use 'sort', each column is sorted individually which is not what I want. Any help would be highly appreciated.
>
> -Faisal

Hi Faisal,

X = [ 1.0000 2.0000 0.4231
1.0000 3.0000 0.8050
1.0000 4.0000 0.7116
2.0000 4.0000 0.6682
2.0000 5.0000 0.4460
2.0000 7.0000 0.5818
3.0000 4.0000 0.0977
3.0000 6.0000 0.5989
3.0000 7.0000 0.3237
4.0000 7.0000 0.2882
5.0000 6.0000 0.1456
5.0000 7.0000 0.3168
6.0000 7.0000 0.2767];
[Y,I] = sort(X(:,3),'descend');
X1 = X(I,:);
% Now look at X1

Wayne
From: Faisal Ahmed on 26 Jul 2010 12:31
Thank you very much Wayne. Problem Solved !
From: us on 26 Jul 2010 12:44
"Faisal Ahmed" <fap87(a)yahoo.com> wrote in message <i2kd8p$9r0$1(a)fred.mathworks.com>...
> Thank you very much Wayne. Problem Solved !

well... yes, but considering the ease of

r=sortrows(X,-3); % <- one simple line...
isequal(X1,r)
% ans = 1

us
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