Subsets In Gams

[/\ l_ !]

Hello Everybody
Thank You For Reading My Question
I Have A Set Of Cities In My Model And The Cities Are Denoted By "i"
and "j"
My Model Outcome Is A Parameter x(i,,j) Which Is A Binary Variable And
For Some "i' and "j"s It Is 1.
How Can I Define A Subset Of The Original Set That Contains The "i"
and "j"s That Their x(i,j) Is Equal To 1.
To Make It More Clear Suppose I Have A Set Of Cities From 1 to 20.
The Model Answers x(i,j) Are x(1,2)=1 x(3,4)=1 And The Rest Are Equal
To 0.
How Can I Define A Subset Of The Original Set Which Becomes {1,2,3,4}
When The Answers Are Like Above?

[Muhajir]

Hi Ali,

I would suggest you use only one set for the cities and create a subset to use in the parameter

**Define set of cities as:
set i  /1*20/
**Define subsets on set i as:
set j(i)/1*20)
set k(i) /1*4/
**Now you can define whatever parameter you want over the subsets like
Parameter x(k,j)
Parameter y(k)

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[Arne Stolbjerg Drud]

Hi Ali

Try something like

Set i / 1*20/;
Alias (i,j);
Binary variable x(i,j);
Set k(i)
..solve model...

k(i)$sum(j,x.l(i,j)) = yes;
k(j)$sum(i,x.l(i,j)) = yes;

The first assignment finds the elements where there is something in the
column of x(I,j) and the second finds the elements where there is something
in the row.

Good luck

Arne

-------------------------------------------
Arne Stolbjerg Drud
ARKI Consulting & Development A/S
Bagsvaerdvej 246A, DK-2880 Bagsvaerd, Denmark
Phone: (+45) 44 49 03 23, Fax: (+45) 44 49 03 33, email: ad...@arki.dk

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af /\ l_ !
Sendt: 7. oktober 2011 11:19
Til: gamsworld
Emne: Subsets In Gams

--

[Matthes]

if you want a one dimensional set, you could try this:

set
z(i)
;
loop((i,j)$(x.l(i,j)=1),
z(i) = yes;
z(j) = yes;
);

[Matthes]

set
z(i,j)
;
z(i,j)$(x.l(i,j)=1) = yes;

On 7 Okt., 05:19, "/\\ l_ !" <ali.ghafoori...@gmail.com> wrote:

[/\ l_ !]

Thanks To Everybody