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

• 

  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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