3

I've tried running this code, but I keep getting the same errors, no matter how much I simplify it.

/home/runner/.site-packages/symfit/core/fit.py:1046: RuntimeWarning: divide by zero encountered in true_divide W = 1/sigma**2/s_sq[:, np.newaxis]

/home/runner/.site-packages/symfit/core/fit.py:1783:> RuntimeWarning: invalid value encountered in double_scalars return 1 SS_res/SS_tot

Help would be greatly appreciated.

x1, ya = sf.variables('x1, ya')
I1, I2, I3, A, B, C, D = sf.parameters('I1, I2, I3, A, B, C, D')


I1.value = 46.483
I2.value = 5.916
I3.value = 21.90
A.value = -3.828*10**(-5)
B.value = 0
C.value = 0
D.value = 0

# Making the equation
ya = (A*x1**3 + B*x1**2 + C*x1 + D + (q_subm*x1**4)/(24*EI))  #q_sub and EI are constants

#model = Model({y: Piecewise((ya, x1 <= I1), (yb, x2 <= I2), (yc, x3 <= I3))})
model = Model({ya})

# As a constraint, we want cable to be at 0 at start and and at "-p" height at x=60
# also no angle in pipe ate those points
constraints = [
    Eq(ya.subs({x1: 0}), 0),
    Eq(ya.subs({x1: 60}), -p),
    Eq(ya.diff(x1).subs({x1: 0}), 0),
    Eq(ya.diff(x1).subs({x1: 60}), 0)
]


x1data = np.linspace(0, 60., 60)
y1data = model(x1=x1data, A = -3.828*10**(-5), B = 0, C = 0, D = 0)
np.random.seed(2)
y1data = np.random.normal(y1data, 0.005) 

plt.plot([60], [0.4], 'ro')
plt.scatter(x1data, y1data)
plt.savefig('plot.png')

print ('Done plotting fig')

#fit = Fit(model, x=xdata, y=ydata, constraints=constraints)
fit = Fit(model, x1=x1data, constraints=constraints)

print ('Done fitting model')
fit_result = fit.execute()
#print(fit_result)
Community
  • 1
  • 1
Ronald Schotman
  • 31
  • 3

1 Answers1

1

I have a few comments about your code, perhaps one of them will solve the problem.

  • model = Model({ya}) wrongfully attempts to make a model from a set, since {} makes a set. Try using model = Model({y: ya}) or model = Model(ya) instead. (I would recommend the first one)
  • The commented line fit = Fit(model, x=x1data , y=y1data, constraints=constraints) is essentially correct, note that I changed the names of the data arrays to include the 1. The line in your example above can't work since you are not providing the ydata.
  • What are the type of q_subm and EI? As long as they are a standard python number type it's fine, but if they are something exotic this might lead to problems.
  • Bare in mind that the "errors" you listed in the question are Warnings, and there is nothing wrong with some warnings during fitting as long as the result is correct.

I hope this solves the problem, if not let me know.

x1, y = sf.variables('x1, y')
I1, I2, I3, A, B, C, D = sf.parameters('I1, I2, I3, A, B, C, D')


I1.value = 46.483
I2.value = 5.916
I3.value = 21.90
A.value = -3.828*10**(-5)
B.value = 0
C.value = 0
D.value = 0

# Making the equation
ya = (A*x1**3 + B*x1**2 + C*x1 + D + (q_subm*x1**4)/(24*EI))  #q_sub and EI are constants
model = Model({y: ya})

# As a constraint, we want cable to be at 0 at start and and at "-p" height at x=60
# also no angle in pipe ate those points
constraints = [
    Eq(ya.subs({x1: 0}), 0),
    Eq(ya.subs({x1: 60}), -p),
    Eq(ya.diff(x1).subs({x1: 0}), 0),
    Eq(ya.diff(x1).subs({x1: 60}), 0)
]


x1data = np.linspace(0, 60., 60)
y1data = model(x1=x1data, A=-3.828*10**(-5), B=0, C=0, D=0)
np.random.seed(2)
y1data = np.random.normal(y1data, 0.005) 

plt.plot([60], [0.4], 'ro')
plt.scatter(x1data, y1data)
plt.savefig('plot.png')

print ('Done plotting fig')

fit = Fit(model, x=x1data, y=y1data, constraints=constraints)
fit_result = fit.execute()

print ('Done fitting model')
print(fit_result)
tBuLi
  • 2,295
  • 2
  • 16
  • 16