PROC OPTMODEL Var statement index specification

[ilikesas]

Hi,

I am working on SAS mathematical programming examples (more precisely ch 7 in https://support.sas.com/documentation/cdl/en/ormpex/64980/PDF/default/ormpex.pdf) with PROC OPTMODEL.

 Here is a part of the VAR statements:

var IsOpen {MINES, YEARS} binary;
var IsWorked {MINES, YEARS} binary;
var Extract {mine in MINES, YEARS} >= 0 <= extract_ub[mine];

My question is why for the VAR EXTRACT are added the words "mine in", unlike the VARS above it, and how could I know whether I should add such specifications.

Thank you!

[RobPratt · Accepted solution]

The dummy indices are optional in the first two VAR statements.  For example, if you prefer you could write the first one as follows:

var IsOpen {mine in MINES, year in YEARS} binary;

The dummy index is required for the third VAR statement because the upper bound extract_ub[mine] depends on it.

[ilikesas]

So if I understand correctly, on p.83:

num discount {year in YEARS} = 1 / (1 + &discount_rate)^(year - 1);

here we have "year" in YEARS becasue there is also "year" on the RHS, whereas for:

proc optmodel;
set <str> MINES;
num cost {MINES};
num extract_ub {MINES};
num quality {MINES};
read data mine_data into MINES=[mine] cost extract_ub quality;

here for the num cost, extract_ub and quality there is no "mine" in MINES becasue there is no RHS part of an equation where "mine" is specified, but here the values are just being read.

[RobPratt]

Yes, that is correct.