how can i write equation at the pic?

gams dosent allow this "d(i,s).. 2*x(i,s,2)+x(i,s+1,1)+ x(i,s+1,2) =l= 2;"

## help about an equation

### Re: help about an equation

Hi,

Looks as if you want to refer to a particular set element explicitly in the third index position of x. In that case, set elements (aka labels) must be quoted.

Helping you would become a lot easier if you share your code such that users can reproduce the exact issue. Just saying GAMS doesn't allow some equation syntax may lack important context.

Fred

Looks as if you want to refer to a particular set element explicitly in the third index position of x. In that case, set elements (aka labels) must be quoted.

Helping you would become a lot easier if you share your code such that users can reproduce the exact issue. Just saying GAMS doesn't allow some equation syntax may lack important context.

Fred

### Re: help about an equation

thanks a lot. i am just a beginner about GAMS. so i will be very thanksfull about any help

here is the my model

set

i hemsire numarası /1*20/

j gün numarası /1*30/

s /1*29/

k vardiya numarası /1*2/

w hafta sonu /1,2,8,9,15,16,22,23,29,30/

v hafta içi /3,4,5,6,7,10,11,12,13,14,17,18,19,20,21,24,25,26,27,28/

;

variables

x

z amaç fonk;

binary variables

x

;

equations

cost

a(j,k) her gündüz-gece vardiyasında en az 4 hemşire bulunsun

b(i,k) her hemşire ayda en az 4 hafta içi gündüz-gece vardiyasında çalışsın

c(i,k) her hemşire ayda en az 2 hafta sonu gündüz-gece vardiyasında çalışsın

d(i,s)

;

cost .. z =e= sum((i,j,k), x(i, j, k)) ;

a(j,k) .. sum((i), x(i,j,k)) =g= 4;

b(i,k).. sum((v), x(i,v,k)) =g= 4;

c(i,k).. sum((w), x(i,w,k)) =g= 2;

d(i,s).. 2*x(i,s,2)+x(i,s+1,1)+ x(i,s+1,2) =l= 2;

model ornek1/all/;

solve ornek1 using MIP minizing z;

display x.l, z.l;

here is the my model

set

i hemsire numarası /1*20/

j gün numarası /1*30/

s /1*29/

k vardiya numarası /1*2/

w hafta sonu /1,2,8,9,15,16,22,23,29,30/

v hafta içi /3,4,5,6,7,10,11,12,13,14,17,18,19,20,21,24,25,26,27,28/

;

variables

x

z amaç fonk;

binary variables

x

;

equations

cost

a(j,k) her gündüz-gece vardiyasında en az 4 hemşire bulunsun

b(i,k) her hemşire ayda en az 4 hafta içi gündüz-gece vardiyasında çalışsın

c(i,k) her hemşire ayda en az 2 hafta sonu gündüz-gece vardiyasında çalışsın

d(i,s)

;

cost .. z =e= sum((i,j,k), x(i, j, k)) ;

a(j,k) .. sum((i), x(i,j,k)) =g= 4;

b(i,k).. sum((v), x(i,v,k)) =g= 4;

c(i,k).. sum((w), x(i,w,k)) =g= 2;

d(i,s).. 2*x(i,s,2)+x(i,s+1,1)+ x(i,s+1,2) =l= 2;

model ornek1/all/;

solve ornek1 using MIP minizing z;

display x.l, z.l;

### Re: help about an equation

Hi,

As indicated in my previous post and by the first error message
set elements must be quoted. After changing equation d to
the model solves.

I hope this helps!

Fred

As indicated in my previous post and by the first error message

Code: Select all

```
*** Error 145 in ...\new1.gms
Set identifier or quoted element expected
```

Code: Select all

```
d(i,s).. 2*x(i,s,'2')+x(i,s+1,'1')+ x(i,s+1,'2') =l= 2;
```

I hope this helps!

Fred

### Re: help about an equation

thanks a lot it was what i need for solve it. have a good day

### Re: help about an equation

i am so sorry but can i ask one more question

how can i assign x(1,3,2) to 1?

guess x('1','3','2')=1; dosent match what i want

how can i assign x(1,3,2) to 1?

guess x('1','3','2')=1; dosent match what i want

### Re: help about an equation

Hi,

A variable has several attributes: https://www.gams.com/latest/docs/UG_Var ... Attributes

You need to specify which one you would like to use, e.g.

to set the variable's level to 1 or

to fix the variable at 1 (upper and lower bound set to 1).

A variable has several attributes: https://www.gams.com/latest/docs/UG_Var ... Attributes

You need to specify which one you would like to use, e.g.

Code: Select all

`x.l('1','3','2')=1;`

Code: Select all

`x.fx('1','3','2')=1;`

### Re: help about an equation

thanks a lot again and again