0

My code is working right except when i enter r1 into the function equation below 

def u(Substrate):         
    return((u_max*ys[:,0])/(Ks+ys[:,0]))


biomass = ys[:,1]    
u = u(ys[:,0])

def r1(u,biomass):
    r1 = u*biomass*YieldCO2_1
    return r1

r1 = r1(u,biomass)

def F(y,t):    
    Ptot = 710
    Vgas = 2
    D = 0.00826*(273.15+Temp)    
    Cstar_CO2 = KH_CO2 * y[2]
    Cstar_CH4 = KH_CH4 * y[3]
    TG_CO2 = KLa_CO2*(Cstar_CO2-y[0])
    TG_CH4 = KLa_CH4*(Cstar_CH4-y[1])
    Q_CO2 = -D*V*TG_CO2
    Q_CH4 = -D*V*TG_CH4
    Qgas = (Q_CO2+Q_CH4)+Q
    F=np.zeros(4)
    F[0] = Q/V * (CO2_To-y[0]) + TG_CO2 + r1
    F[1] = Q/V * (CH4_Do-y[1]) + TG_CH4 
    F[2] = -Ptot*D*TG_CO2*(V/Vgas)-y[2]*(Qgas/Vgas)
    F[3] = -Ptot*D*TG_CH4*(V/Vgas)-y[3]*(Qgas/Vgas)
    return F 

yinit = np.array([4,3,250,200])             
ts = np.arange(0,4,0.4)  
y = odeint(F,yinit,ts)

When r1 is seen in equation F[0] I get the following error:

F[0] = Q/V * (CO2_To-y[0]) + TG_CO2 + r1
ValueError: setting an array element with a sequence.
odepack.error: Error occurred while calling the Python function named F

However when I do the function without the r1 array, there is no error. so that is why i am assuming something is wrong with putting the r1 array into the function If anyone could provide input to my problem i would

Improve this question
2
  • Maybe F should be F = np.zeros((4, len(r1))
    – Bi Rico
    Commented Mar 22, 2013 at 14:50
  • You are clobbering names all over the place. E.g u = u(ys[:,0]), r1 = r1(u,biomass), using F as a variable in a function called F. You should not use variable names that are the same as the function names. It makes your code difficult to understand and difficult to debug.
    – Warren Weckesser
    Commented Mar 22, 2013 at 15:47

1 Answer 1

Reset to default
1

F[0] = expression expects expression to be a number here, not an array. However Q/V * (CO2_To-y[0]) + TG_CO2 + r1 is an array of r1 dimensions. To see this, try evaluating the following line:

>>> 1 + numpy.array([1,2])
array([2, 3])

To get rid of the exception you should covert this expression to a number somehow depending on what you are trying to achieve.

Improve this answer
3
  • Thank you for such a quick response! A number? what i am trying to achieve is the functions are differential equations that vary per time. i am solving for the y values, y[0], y[1], y[2], and y[3].There should be different values of y's for each time variable.
    – user2199360
    Commented Mar 22, 2013 at 14:52
  • Yes, but each time you assign a value to F[0], that value must be a scalar. Apparently the expression you are assigning to F[0] is not a scalar.
    – Warren Weckesser
    Commented Mar 22, 2013 at 15:50
  • @user2199360, Q/V * (CO2_To-y[0]) + TG_CO2 is a number, r1 is a numpy array, so their sum is a numpy array. But F[0] is a scalar. What you can do is use r1[0] or sum(r1) - actual approach depends on your needs.
    – Andrei
    Commented Mar 22, 2013 at 15:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.