CODEWITHSUNDEEP
loopsmappinggams-math
Michael
Michael

Reputation: 575

Calculation with mapping in GAMS

Consider the following data:

set i    / 1 * 4      /
    tid  / 2019, 2020 /
    iagg / 1 * 2      /;
parameter t(i,tid),tagg(iagg,tid);

t(i,tid) = uniform(0,1);

set itoiagg(i,iagg) /
    1.1
    2.1
    3.2
    4.2
/;

I want to do the following calculation the aggregated set (iagg):

tagg("1","2020") = (t("1","2020")/t("1","2019")*(t("1","2019")/(t("1","2019")+t("2","2019")))) +
                   (t("2","2020")/t("2","2019")*(t("2","2019")/(t("1","2019")+t("2","2019"))));

In this simple case, I could also do it for the second iagg:

tagg("2","2020") = (t("3","2020")/t("3","2019")*(t("3","2019")/(t("3","2019")+t("4","2019")))) +
                   (t("4","2020")/t("4","2019")*(t("4","2019")/(t("3","2019")+t("4","2019"))));

But I have a big dataset, so is there an easy way where I can do this calculation using a loop or something like that?

Upvotes: 0

Views: 65

Answers (1)

Lutz
Lutz

Reputation: 2292

What about this:

set i    / 1 * 4      /
    tid  / 2019, 2020 /
    iagg / 1 * 2      /;
parameter t(i,tid),tagg(iagg,tid);

t(i,tid) = uniform(0,1);

set itoiagg(iagg,i) /
    1.1
    1.2
    2.3
    2.4
/;

tagg(iagg,tid)$(ord(tid)>1) = sum(itoiagg(iagg,i),  (t(i,tid)/t(i,tid-1)*(t(i,tid-1)/(t(i,tid-1)+t(i,tid-1)))));

Sidenote: I turned around the indices of itoiagg in the assignment, since it is generally avisable to reference indices in the order they are controlled in GAMS. That could make a performance difference, if the data gets large.

Upvotes: 1

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