## Newton's Method Issues

### SB (view profile)

on 19 Nov 2012

Hi, I'm having a little trouble with my newton's method code.

One of my biggest issues is that I'm not able to create an output, rHist, which is a vector consisting of x0 and the outputs after every iteration of newton's method and my number of iterations is off by 1.

My code (posted below) also doesn't seem to work when the initial guess, x0 satis fies the stopping criterion.

``` % function [r,N,fRoot] = newtonRaphE7(fHan,dfHan,x0,fTol,iterMax)
k=1;
while k<=iterMax
x=x0-fHan(x0)/dfHan(x0)
if abs(x-x0)<fTol*abs(x)
return
x0=x;
r=x0;
k=k+1;
N=k;
fRoot=abs(fHan(r));
end
end```

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### Matt J (view profile)

on 19 Nov 2012

It should contain lines like this somewhere

` rHist=zeros(1,iterMax+1);`
```....
```
` rHist(k)=x;`

My code (posted below) also doesn't seem to work when the initial guess, x0 satis fies the stopping criterion.

Because you're exiting without updating the outputs r,N, fRoot

Matt J

### Matt J (view profile)

on 19 Nov 2012

It doesn't do any good to put them at the end if the code never reaches the end, and it doesn't, because you call RETURN before it gets there.

SB

### SB (view profile)

on 19 Nov 2012

Alright, how would I actually rewrite it, just move the statements after the if?

Matt J

### Matt J (view profile)

on 19 Nov 2012

Hint: MATLAB executes lines of code in order from top to bottom.

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