Subset from a one-to-many set

[Baden]

I have some very large sets, and would like to make some subsets.
Here I try to describe it, by they same (but smaller) sets

Sets
I "farmers" /1*5/
M "fields" /1*20/
conventional(I) /1,2,4/
organic(I) /3,5/
Ifield(I,M) "farmer I is owner of field(s)"
/1.(1,2)
2.(3,4,6,7,8,9)
3.(10)
4.(11,12,13,14,15,16,17)
5.(18,19,20) /

Then I would like to make a subset of fields which are organic 'organic(M)' and
one which is conventionel 'conventionel(M)' I need to have them as (M)
and not as (I,M). But I can't make it work.

Sets
organic(M)
conventionel(M) ;

organic(M) = ?
conventionel(M) = ?

Keep getting errors like; 'dimension different', 'Uncontrolled set entered as constant' etc .

:-/ Baden

[Dol, Wietse]

Hi Baden,

Yes its always a puzzle... Basically you could see a set as a parameter that only takes the values 1 and 0. Then you just need the right summation and multiplication... DId you want the following:

Sets
I "farmers" /1*5/
M "fields" /1*20/
conventional(I) /1,2,4/
organic(I) /3,5/
Ifield(I,M) "farmer I is owner of field(s)"
/1.(1,2)
2.(3,4,6,7,8,9)
3.(10)
4.(11,12,13,14,15,16,17)
5.(18,19,20) /

Sets
organicfields(M)
conventionelfields(M) ;

OrganicFields(M) $sum(I,Ifield(I,M)*organic(I)) =yes;
ConventionelFields(M)$sum(I,Ifield(I,M)*conventional(I))=yes;

display organic,conventional;
display OrganicFields,ConventionelFields;
*Note Field 5 is missing!

Best wishes
Wietse

________________________________________
From: gams...@googlegroups.com [gams...@googlegroups.com] On Behalf Of Baden [jeppe...@gmail.com]
Sent: Thursday, February 09, 2012 3:50 PM
To: gams...@googlegroups.com
Subject: Subset from a one-to-many set

Sets
organic(M)
conventionel(M) ;

:-/ Baden

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[Baden]

Perfect!

That works just they way that I need. And I also learned a lot. So big thanks!

And yes, typo with the field 5

best regards
baden