How can I restrict a variable that can only take value in a list？

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Morris Lin

2022年09月16日 09:06

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list1=[1,2,3,4];

i want a variable that can only take value in that list

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  Simranjit Kaur

  • Gurobi Staff

  2025年11月16日 23:28

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Marika Karbstein

  • Gurobi Staff

  2022年09月16日 09:29

  It is not possible to give an arbitrary list that indicates the allowed values of a variable.
  If your variable is only allowed to take a value 1,2,3, or 4, you could define an integer variable with lower bound 1 and upper bound 4.

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  Jonasz Staszek

  • Community Moderator

  2022年09月22日 13:39

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  Dear Marika, dear Morris,

  as a workaround, one can try to use indicator variables and constraints to model the desired behaviour (have a look here for an example). This will most likely not scale well though.

  Best regards
  Jonasz

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  Morris Lin

  2022年09月23日 08:41

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  Thank for Jonasz's help.

  I have a idea to achieve it. Using indicator variables and limiting x like (0.9999<=x<=1.0001)&(1.9999<=x<=2.0001)...

  There's a similar problem that bothers me. I post it below.

  x only can equal 1 or 2 or 3 or 4

  y only can equal 2 or 3 or 4 or 5，y is related to x. 

  for example, x==1, y==2 or x==2, y==3 or ...

  And I usually code in matlab, it is hard to express the above by martix.

   

   

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