CODEWITHSUNDEEP
gams-math
merija
merija

Reputation: 215

In GAMS, how do I replace an index with a parameter?

Sets  
i / 1, 2 /;

Parameters 
j(i) / 2, 1 /;

Variables 
x(i);

So, here I have an index i, a parameter that depends on i which gives the same values as i, and a variable that depends on x.

If I want to get x(2), I could of course write x(2), but what if I wanted to write x(j(1)). Since j(1) = 2, this ought to be the same, but GAMS doesn't like it, and says it expected a set.

How can I do this?

Upvotes: 0

Views: 560

Answers (2)

Jon
Jon

Reputation: 371

You could use a mapping: see example below which maps x(1) to P(2) and x(2) to P(1), using the mapping j which maps 1 to 2 and 2 to 1.

Set i / 1, 2 /;
alias(k,i);

set j(i,k) /
1.2
2.1
/;

parameter P(i);
P("1") = 10;
P("2") = 20;

Variables
x(i);

loop(j(i,k),  x.l(k) =P(i));

execute_unload "test.gdx";

Upvotes: 1

GFA
GFA

Reputation: 86

Not sure if I understand the question correctly, but maybe you just mean x(i) = j(i) ? Then for all set elements of i x will take the same value of j. If you only want the first set element: x("1") = j("1"). j("1") = 2, so x("1") will equal 2 too.

Upvotes: 0

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