forum.alglib.net

Hello all,

I am new to alglib, but I am getting the hang of it pretty quickly. Well done! I am trying to write a program that models some data with a 6th order polynomial. I am trying to get a good fit, and I have modeled this data in excel, however in excel I can put a Y intercept on my polynomial trend line.

My question is: How do I specify a Y-intercept of '0' with alglib? I am writing the code in C#

Thanks!
Jameson

In the VBA version, the PolynomialFitWC routine allows fitting with constraints and weights, which will allow you to do what you want. There is an Excel based version available here:

http://newtonexcelbach.wordpress.com/20 ... functions/

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Doug Jenkins
http://newtonexcelbach.wordpress.com/

I'm not familiar with the polynomialfitwc function. What parameters do I need to put in there to get it to intercept at 0?

Have you looked at the manual?

http://www.alglib.net/translator/man/ma ... omialfitwc

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Doug Jenkins
http://newtonexcelbach.wordpress.com/

Yes, I have thoroughly read about the Polynomialfitwc function. I believe I have it correct now. I have my XC and YC values as an array of only one element to make my function's Y = 0 at X =0.

double XC[] = {0};
double YC[] = {0};

I am wondering if each element in the XC array corresponds to the same index in the X array. What happens when I add more values to the arrays?

No, there is no correspondence between XC and X arrays (or Y and YC arrays). There is one-to-one correspondence between X and Y, XC and YC.