## Meaning of polyfitting coeffs

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Yacu
Newbie
Posts: 31
Joined: Tue Dec 23, 2008 12:00 am

### Meaning of polyfitting coeffs

I'm implementing a polyfitting function to a curve. The Chart works beautifully on an example but if I compute the values wiht the polyfitting coefficients I get strange numbers.
The question is: Are the coefficients normalized?, do I have to apply a transformation? or anything.

I get the following equation

y= +4.8117 -2.5595*x +0.3412*x^2

The chart data gives you the reading Y=5.057 for X=3. However, If you apply the above equation, you get Y= 0.204 for X=3

My question is Where is the trick?, How do you apply the coefficients and explain the difference?. Maybe you have some written documentation on the method used for fitting the curve and the meaning of the coeficients

Thank you

Christopher
Posts: 1349
Joined: Thu Jan 01, 1970 12:00 am
Location: Riudellots de la Selva, Catalonia
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### Re: Meaning of polyfitting coeffs

Yacu,
Yacu wrote: My question is Where is the trick?, How do you apply the coefficients and explain the difference?. Maybe you have some written documentation on the method used for fitting the curve and the meaning of the coeficients
There's a thread discussing this issue which I strongly recommend you read here. I hope this is of some help!
Thank you!

Christopher Ireland (Steema crew)
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