How to add equation containing decision variable into an array.

Answered

Thunwa Wanphian

June 14, 2022 08:29

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I got a problem to store the equation containing the decision variable into an array.

Here, This is my code and noted that y[j,k] is my binary decision variable. 

Time_span = 16
Expo_noise_matrix = range(1,Time_span+1)
Times = range(1,Time_span+1)

for k in Times:
    Expo_noise_matrix[k] = ((70*y[1,k]+60*y[2,k]+80*y[3,k])*(1-((-1+y[1,k]+y[2,k]+y[3,k])*0.2)))

The error showed this,

      3 for k in Times:
----> 4     Expo_noise_matrix[k] = ((70*y[1,k]+60*y[2,k]+80*y[3,k])*(1-((-1+y[1,k]+y[2,k]+y[3,k])*0.2)))

TypeError: 'range' object does not support item assignment

I need to store those decision variable equations in array to call and calculate the objective function next.

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 16, 2025 23:34

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• 

  Jaromił Najman

  • Gurobi Staff

  June 15, 2022 07:38

  In your code \(\texttt{Expo_noise_matrix}\) is a range object and thus, you cannot assign values to it.

  You should rather use a dictionary for \(\texttt{Expo_noise_matrix}\).

  Time_span = 16
  Expo_noise_matrix = {}
  Times = range(1,Time_span+1)
  
  for k in Times:
      Expo_noise_matrix[k] = ((70*y[1,k]+60*y[2,k]+80*y[3,k])*(1-((-1+y[1,k]+y[2,k]+y[3,k])*0.2)))

  Best regards, 
  Jaromił

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• 

  Thunwa Wanphian

  June 15, 2022 07:54

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  Dear: Jaromił

  It's work now, thank you :).

  Best regards,

  Thunwa.

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