Need help fixing Index Error

[adesimone]

Hi,

This is for a class project. The course is not a coding course, but we do use code to complete homework and projects (yes, it is as confusing as it sounds). Because of this, we are allowed to ask for outside help.

I am receiving an IndexError with the following code. I cannot figure out why the for loop is breaking. I've tried debugging multiple times but still cannot find which scalar variable the code is upset about. I call a function "values" within it - I do not believe that code is necessary for fixing this error.

I am trying to optimize "values" using the following arrays. Suggestions for a more efficient way of optimization would be helpful!

iteration = 40
Ltotal = np.linspace(1,20000,iteration) #m
m = np.linspace(1,40,iteration) #number of passes
ktube = np.array([400,48,160,16]) #copper,mild steel, aluminum, stainless steel
Cptube = np.array([376.8,510.8,921.1,460.5])
ptube = np.array([894,785,270,800] )
tfin = np.linspace(0.1/1000,1/1000,iteration) #m
tspace = np.linspace(1/1000,1/100,iteration) #m
ODtube = np.linspace(0.0001,1,iteration) #m
unitcost = np.array([7.50,0.34,1.87,1.98]) #$/kg

for j in range(len(ktube)):
    for i in range(iteration):
        Qtotal,effectiveness,U,Ltotal,Twaterout,Tairout,cost = values(Ltotal[i],m[i],ktube[j],Cptube[j],ptube[j],tfin[i],tspace[i],ODtube[i],unitcost[j])
        if 82000<=Qtotal<=87000:
            if j == 0:
                print('copper,Q = {}'.format(Qtotal))
            if j==1:
                print('mild steel, Q = {}'.format(Qtotal))
            if j==2:
                print('aluminum, Q = '.format(Qtotal))
            else:
                print('stainless steel, Q = {}'.format(Qtotal))
        else:
            print('option {} doesnt work Q = {}'.format(i,Qtotal))
            i+=1

Here is the error:

Error:
    Qtotal,effectiveness,U,Ltotal,Twaterout,Tairout,cost = values(Ltotal[i],m[i],ktube[j],Cptube[j],ptube[j],tfin[i],tspace[i],ODtube[i],unitc2\designreport2.py", line 179, in <module>ost[j])                                                                l[i],m[i],ktube[j],Cptube[j],ptube[j],tfin[i],tspace[i],ODtube[i],unitcost[j])
IndexError: invalid index to scalar variable.

[deanhystad]

This returns the same error.

import numpy as np
x = np.array((1, 2, 3))
y = x[1]
z = y[1]

Error:
  File "test.py", line 4, in <module>
    z = y[1]
IndexError: invalid index to scalar variable.

This indicates that something that is not indexable is being indexed. In particular it means a numpy scalar is being indexed because you get a different error message if you index an int or a float.

But I don't see where this is happening in your code. I did this as a quick check.

import numpy as np

iteration = 40
Ltotal = np.linspace(1,20000,iteration) #m
m = np.linspace(1,40,iteration) #number of passes
ktube = np.array([400,48,160,16]) #copper,mild steel, aluminum, stainless steel
Cptube = np.array([376.8,510.8,921.1,460.5])
ptube = np.array([894,785,270,800] )
tfin = np.linspace(0.1/1000,1/1000,iteration) #m
tspace = np.linspace(1/1000,1/100,iteration) #m
ODtube = np.linspace(0.0001,1,iteration) #m
unitcost = np.array([7.50,0.34,1.87,1.98]) #$/kg

i = 0
j = 0
print(Ltotal[i],m[i],ktube[j],Cptube[j],ptube[j],tfin[i],tspace[i],ODtube[i],unitcost[j])

That ran with no problems, leaving this:

values(Ltotal[i],m[i],ktube[j],Cptube[j],ptube[j],tfin[i],tspace[i],ODtube[i],unitcost[j])

What is values()?