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+--- Thread: ValueError in function (/thread-10977.html)
ValueError in function - Tipillo - Jun-16-2018
Hi, I would like to know how I can improve my function so that I do not trigger the ValueError exception when I do the following(its an implementation of Newton-Raphson):
import sys
import sympy as sy
def newt(x, fx, x0, precision, iterations):
import numpy as np
# Initial Error
e = np.inf
dfdx = fx.diff(x)
xini = x0
j = 1
r = 0
while(j<=iterations):
xsig = xini - (float(fx.subs(x, xini)) / float(dfdx.subs(x, xini)))
xsig = float(xsig)
if ((abs(xsig-xini)/abs(xini)) < precision):
r = xsig
iterations = j
e = (abs(xsig-xini)/xini)
return dfdx, r, iterations, e
j+=1
xini = float(xsig)
print ("The method fails after: %s" %iterations)
x = sy.Symbol('x')
fx = -26 + 85 * x - 91 * x ** 2 + 44 * x ** 3 - 8 * x ** 4 + x ** 5
dfdx, r, iterations, e = newt(x, fx, 10, 0.0001, 2) #2 iterations to trigger the exception
print('f(x)=', fx)
print("f'(x)=", dfdx)
print('Root ', r, ' calculated after ', iterations, ' iterations')
print('Error ', e)Thanks
RE: ValueError in function - Larz60+ - Jun-16-2018
Please be more specific. Where exactly is the ValueError being issued, any example?
Once identified, you can use a try, except block to take proper action when a value error is encountered.
RE: ValueError in function - ichabod801 - Jun-16-2018
Your function does not return anything, so you get a value error when you try to assign it to a tuple. You need a return statement with the four things you're trying to get out of it on line 28.