how can I retrieve the values for a single variable? The variable is something like d(b,t).

Answered

Yiwen Zhou

• August 24, 2019 21:43

Hi,

The command model.getVars() shows the values of all the variables. Can I only get the values of a certain variable? Because I would like to make some graphs to show its values varying with time.

The variables are set up as follows: (but I also have many other variables)

l = m.addVars(G,T , name="load")
d = m.addVars(N,T, name="d")

The related constraints are set up like as follows:

for g in G:
    for t in T1:
          m.addConstr((l[g, t] - l[g, t-1] <= gen_ramp_up[g] ), "{} ramp up".format(g,t))

 

Is there any command that could help to retrieve only the values of "l"?

 

Thanks so much!

 

0

• Official comment

  

  Simranjit Kaur

  Gurobi Staff

  • December 06, 2024 00:54

  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 why not try our AI Gurobot?.
• 

  Eli Towle

  Gurobi Staff

  • August 26, 2019 13:47

  Hi Yiwen,

  The variable l is a tupledict that maps a set of indices to Var objects. The values() method of a tupledict returns a list of the corresponding Var objects. Finally, the X attribute of a Var object stores the variable's value at the current solution.

  So, after optimizing, you can iterate through each variable in the tupledict and retrieve the variable's solution value. For example:

  for v in l.values():
      print("{}: {}".format(v.varName, v.X))

  You could also use a dictionary comprehension to construct a dictionary that maps the variable indices to the corresponding solution values. This can be done by iterating over the tupledict's key-value pairs:

  vals = { k : v.X for k,v in l.items() }

  I hope this helps!

  1
• 

  Yiwen Zhou

  • August 26, 2019 14:45

  

  

  

  Thanks a lot Eli! :-)

  0
• 

  Mai Elgazzar

  • January 29, 2022 23:10

  how can I get the result in one list? 

  as my case is:

  for v in   A.values(): 
      z= (v.X)
      print ((z))

   

  my result is:

  0.0
  361.0
  709.0
  0.0

   

  while I need to have them in one list to be able to do further operations on them

   

  0

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