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 Post subject: LSFitLinear: cubic interpolation
PostPosted: Mon May 31, 2010 10:26 pm 
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Joined: Mon May 31, 2010 10:13 pm
Posts: 1
I'm a newbie with ALGLIB
I'm using a0*x^3+a1*x^2+a2*x+a3 to interpolate data values with LSFitLinear:
x y
46 68
70 120
94 138
95 145
102 165
120 205
I notice wrong result and I have solved the problem scaling input by dividing by 100. What I do wrong?

Regards,

David


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 Post subject: Re: LSFitLinear: cubic interpolation
PostPosted: Thu Jun 03, 2010 7:22 pm 
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Joined: Fri May 07, 2010 7:06 am
Posts: 873
Looks like your problem has very bad condition number. Scaling makes it less apparent but doesn't solve.

I think that right solution is to use Chebyshev polynomials for fitting, than convert to power basis. I'll include this code in the next release of ALGLIB.


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