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Will anyone expain me the basic principle behind the generation of Newton Fractals?

I think I have a basic( and only a very basic) idea of The Newton-Raphson Method, Calculus and Complex Number

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'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Hi;

What expression are they iterating through Newton Raphson?

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**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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They? Who are they?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
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Good question. Is there some function being iterated?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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Actually, this is not something I am being taught at school.

I am just trying to learn it and know about its basics

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Hi;

newton's generates lots of fractals. here is one;

http://upload.wikimedia.org/wikipedia/c … nction.png

Have you read Gleicks book?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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No! What's the name of the book?

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
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"Chaos Making a New Science" by James Gleick

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What is the basic principle behind generation of fractals?

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
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The instability of Newton's iteration is the main thing!

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Whats "instable" about it?

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
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We would have to go over it to really understand that. But I can say that everyone is taught to use it as model of efficiency. Oh, the way it zooms in on the roots of the canned problems that are given it in books.

Truth is unless you get a good initial guess, one that is close to the root in a special Newton's will go haywire.

In short it exhibits sensitivity to initial conditions, the mark of Chaos!

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Chaos is nice!

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

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**bobbym****Administrator**- From: Bumpkinland
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Nope! Chaos is a big mess.

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Why? Don't you enjoy randomness?

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

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**bobbym****Administrator**- From: Bumpkinland
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I am a numerical analyst. I consider that nothing but round off error, algorithm error. We try to eliminate it and Chaoticians are trying to show it, highlight it.

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
- Posts: 3,854

Hi Bobby,

Truth is unless you get a good initial guess, one that is close to the root in a special Newton's will go haywire.

Yes, that's what happens with your towers problem if I use Newton's Method.

I wrote an LB program for it, and unless my initial guess is between 33.886745 and 39.999999, LB goes crosseyed.

```
PROMPT "Enter approx. x (>33.886745 and <39.999999)";x$
x=VAL(x$)
[loop]
a=1/SQR(2500-x^2)+1/SQR(1600-x^2)-1/10
IF ABS(a-z)<0.000000001 THEN PRINT "15-digit approximation of x: ";USING("##.#############",x):END
z=a
b=x/(2500-x^2)^(3/2)+x/(1600-x^2)^(3/2)
x=x-a/b
GOTO [loop]
Output (for input between 33.886745 and 39.999999):
"15-digit approximation of x: 37.3550853341325"
```

*Last edited by phrontister (2012-11-24 01:42:04)*

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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**bobbym****Administrator**- From: Bumpkinland
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Hi;

Newton's has that problem and a few others.

In the case of that program you might try improving it by replacing this line:

IF a=z THEN

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
- Posts: 3,854

Hi Bobby,

I don't understand why that line needs changing.

Would this be better?

IF a-z=0 THEN

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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**bobbym****Administrator**- From: Bumpkinland
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Remember a while back with the loop that counted down from 1 to 0 by .1?

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
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Hmmmm......thinking........still thinking.........and.......nope!

I think you mentioned that case not all that long ago, and I think that I recalled it then. But not now! Grumble.

What was it again? (sorry)

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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The comparison of two floating point numbers for equality is always dangerous.

z = a is a possible problem

Take a look over here and see what I mean:

http://www.mathisfunforum.com/viewtopic … 56#p117156

post #18

**In mathematics, you don't understand things. You just get used to them.**

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
- Posts: 3,854

Ah...yes. I remember that now. *slaps forehead*

When I wrote "IF a=z THEN" I thought that a & z would never actually equal each other (except with an integer solution, maybe?), but I went for that option anyway because I couldn't come up with anything better then, and it happened to halt program execution at the right time.

I still haven't thought of a way to overcome that, and I couldn't glean anything from that past discussion. I probably don't understand it well enough now, although I think I did at the time.

Any hints for this one?

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
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Maybe a FOR/NEXT loop?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Hi;

How about the solution of not testing for equality but test whether they are close

Abs[a-z]<.0005

You can adjust the .0005, it is just for illustration,

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