kgotlele...@galmail.co.za wrote:
Hi,
I am trying to write a program in python that solves a system of nonlinear
equations using newton's method. I don't know what I am doing wrong.
> Please help
In general, it helps for both you and us if you show what happens when you run
the program, and how that is not according to your expectations.
In this case, you just say "I don't know what I am doing wrong".
We can look at the code and see what will happen when one executes it, but we
don't know how that is wrong for you.
from scipy import*
Many readers here (including self) don't know much about numerical stuff, so
if that's your problem, maybe posting at a scipy related list may be more useful.
x = array([0.0,0.0,0.0])
n=len(x)
tol= 0.00001
N=30
k=1
while k <= N:
def f(x):
f= zeros((len(x)),float)
f[0][k]= x[0][k]**2 + x[1][k]-37
f[1][k]=x[0][k]- x[1][k]**2- 5
f[2][k]= x[0][k] + x[1][k]+ x[2][k]- 3
return f[k]
def J(x):
J= zeros((n,n),float)
for i in range(n):
ei=zeros(n,float)
ei[i]=1.0
J[:i]=(f(x[k]+tol*ei)-f(x[k]))/tol
return J
y[k] = -(J.I)*f[k]
x[k+1]=x[k]+y[k]
You have a while loop, and inside the loop you define a function called 'f'.
Can you explain what you think should happen here?
if sqrt(dot(f0,f0)/len(x)) < tol: print x
f0 is never defined above, so you will get an 'undefined identifier f0' error
here.
What is f0 supposed to be?
(if you intended to call 'f' here, type 'f(0)' instead of 'f0')
(Calling f probably makes sense only if the 'if' statement is inside the
'while' loop. See also below.)
else:
k=k+1
The 'if' statement is after the 'while' loop. Incrementing k here does not
make much sense here.
Maybe you meant the 'if' inside the 'while'?
If so, indent the statement accordingly (same amount as the "def f(x):" line).
Albert
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