Hi, i have two questions about sum notation
Think that i have a set
t /1*10/
and i have a binary variable x(t)
questions
1) How can i sum x(t) starting from t=2
2) How can i exclude t values which i want
that is:
I want to say that sum(t, x(t)) =e= 1 BUT i dont want this equation include t=9 and t=10 for example.
Or i want to say that sum(t, x(t)) =e= 1 again BUT starting from t=2 and ending at t=7 while t is /1*10/
Questions about Summation

 User
 Posts: 75
 Joined: 2 years ago
 Location: Rosario  Argentina
Re: Questions about Summation
Hello, you have many alternatives:
sets
t /t1*t10/
;
(1) sum(t$(ord(t) ge 2),x(t))
(2) sum(t$(ord(t) ne 9 and ord(t) ne 10),x(t)) =e= 1
sum(t$(ord(t) ge 2 and ord(t) le 7),x(t)) =e= 1
using subsets:
sets
t /t1*t10/
sum1(t) /t2*t10/
sum2(t) /t1*t8/
sum3(t) /t2*t7/
;
(1) sum(t$sum1(t),x(t))
(2) sum(t$sum2(t),x(t)) =e= 1
sum(t$sum3(t),x(t)) =e= 1
for example, if you want to avoid t=2 and t=6:
sets
t /t1*t10/
avoid(t) /t2,t6/
;
sum(t$(not avoid(t)),x(t)) =e= 1 (includes all t except t=2 and t=6)
Bye!
sets
t /t1*t10/
;
(1) sum(t$(ord(t) ge 2),x(t))
(2) sum(t$(ord(t) ne 9 and ord(t) ne 10),x(t)) =e= 1
sum(t$(ord(t) ge 2 and ord(t) le 7),x(t)) =e= 1
using subsets:
sets
t /t1*t10/
sum1(t) /t2*t10/
sum2(t) /t1*t8/
sum3(t) /t2*t7/
;
(1) sum(t$sum1(t),x(t))
(2) sum(t$sum2(t),x(t)) =e= 1
sum(t$sum3(t),x(t)) =e= 1
for example, if you want to avoid t=2 and t=6:
sets
t /t1*t10/
avoid(t) /t2,t6/
;
sum(t$(not avoid(t)),x(t)) =e= 1 (includes all t except t=2 and t=6)
Bye!