## Equation based on set number

Problems with syntax of GAMS
sinagilassi
User
Posts: 8
Joined: 1 year ago

### Equation based on set number

Hi,

I defined a set and a parameter as

Code: Select all

``````Sets i /1, 2/;

Positive Variable X_V_ce(i);

``````
one of the constraints is

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``````
Z1(i).. X_V_ce(i) =e= X_V_ce(i+1) + ....

``````
How it can be defined, i cannot be set i+1 !!

What can I do to add 1 or 2 to an element?

Regards

Renger
Posts: 221
Joined: 2 years ago

### Re: Equation based on set number

Hi
This is not a problem for Gams. For i = 2, it writes the equation as
Z1(i).. X_V_ce("2") =e= 0;
If you want another formulation for this case, you could use the cardinality of set i (the number of elements):
Z1(i).. X_V_ce(i) =e= X_V_ce(i+1)\$(ord(i) ne card(i) + (.....)\$(ord(i) eq card(i);
Hope this answers your question
Cheers
Renger

sinagilassi
User
Posts: 8
Joined: 1 year ago

### Re: Equation based on set number

Hi Renger,

Thank you for your help
Renger wrote:
1 year ago
Hi
This is not a problem for Gams. For i = 2, it writes the equation as
Z1(i).. X_V_ce("2") =e= 0;
If you want another formulation for this case, you could use the cardinality of set i (the number of elements):
Z1(i).. X_V_ce(i) =e= X_V_ce(i+1)\$(ord(i) ne card(i) + (.....)\$(ord(i) eq card(i);
Hope this answers your question
Cheers
Renger