I want to find the zeros of a simple function for given parameters a, b, c. I have to use the Newton-Raphson method. The problem I obtain when I compile the code is that the x variable is not defined.
from scipy import optimize
def Zeros(a, b, c, u):
return optimize.newton(a*x**2+b*x+c, u, 2*ax+b, args=(a, b, c))
a, b, c are constants of the function f and u is the starting point. So with this function I should be able to obtain a zero by specifying a, b, c and u. For instance:
print Zeros(1, -1, 0, 0.8)
But I obtain "global name 'x' is not defined".
Why does that happen?
The way most programming languages work is that they use variables (the names a, b, c, u in your code) and functions (Zeros, for instance).
When calling a function, Python expects all of the "quantities" that are input to be defined. In your case, x does not exist.
The solution is to define a function that depends on x, for the function and its derivative
from scipy import optimize
def Zeros(a,b,c,u):
def f(x, a, b, c):
return a*x**2+b*x+c
def fprime(x, a, b, c):
return 2*a*x + b
return optimize.newton(f, u, fprime=fprime,args=(a,b,c))
print(Zeros(1,-1,0,0.8))