Using pulp and python I am trying to solve a water balance(similar to the classic transportation problem) linear programming problem in the form of:
minimize c'x subject to:
Ax=b
lb<=x<=ub
where A is a (10x18) matrix, c(1x18) and b(10x1) are vectors and U (18x2) is a two-column matrix that includes lb and ub respectively.
import pulp as p
import pandas as pd
import numpy as np
A=pd.read_csv(r"C:\...\A.csv",delimiter=',',dtype='int8',header=None)
A=A.to_numpy()
c=pd.read_csv(r"C:\...\c.csv",delimiter=',',dtype='float64',header=None)
c=c.to_numpy()
U=pd.read_csv(r"C:\...\U.csv",delimiter=',',dtype='float64',header=None)
b=pd.read_csv(r"C:\...\b.csv",delimiter=',',dtype='float64',header=None)
b=b.to_numpy()
# Create a LP Minimization problem
Lp_prob = p.LpProblem('Problem', p.LpMinimize)
# Create problem Variables
x = p.LpVariable("x", lowBound = U[0], upBound = U[1]) # Create a variable x
# Objective Function
c=np.transpose(c)
Lp_prob+= p.lpSum(c*x)
# Constraints:
Lp_prob += p.lpSum(A*x) == b
# Display the problem
print(Lp_prob)
status = Lp_prob.solve() # Solver
print(p.LpStatus[status]) # The solution status
# Printing the final solution
print(p.value(x), p.value(Lp_prob.objective))
Question When I try to run the project, it displays the message
"File "C:\Users\stavroula\Anaconda3\lib\site-packages\pandas\core\generic.py", line 1555, in nonzero self.class.name
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all()."
Why does it happen?
The problem can be solved successfully using the scipy.optimize.linprog() routine.
Thanks in advance!!
