Hello,
If this is a constraint (for proc optmodel) I need:
 
Constraint Example:Sum{<v,'123','ABC'> in v_l_m}X[v]*M[v,'123','ABC'];
 
.. but the subscript '123' does not exist for all M[v,l,m]'s. (It's not missing, the entry itself has been left out.)
 
How can I avoid the 'invalid array subscript error'?
 
Thanks&kind regards