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| Polynomialfit Y intercept http://forum.alglib.net/viewtopic.php?f=2&t=421 |
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| Author: | jamdaman5000 [ Thu Aug 25, 2011 10:04 pm ] |
| Post subject: | Polynomialfit Y intercept |
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 |
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| Author: | Doug Jenkins [ Fri Aug 26, 2011 4:25 am ] |
| Post subject: | Re: Polynomialfit Y intercept |
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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| Author: | jamdaman5000 [ Fri Aug 26, 2011 1:29 pm ] |
| Post subject: | Re: Polynomialfit Y intercept |
I'm not familiar with the polynomialfitwc function. What parameters do I need to put in there to get it to intercept at 0? |
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| Author: | Doug Jenkins [ Sat Aug 27, 2011 10:13 am ] |
| Post subject: | Re: Polynomialfit Y intercept |
Have you looked at the manual? http://www.alglib.net/translator/man/ma ... omialfitwc |
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| Author: | jamdaman5000 [ Tue Aug 30, 2011 4:13 pm ] |
| Post subject: | Re: Polynomialfit Y intercept |
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? |
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| Author: | Sergey.Bochkanov [ Mon Sep 05, 2011 4:06 pm ] |
| Post subject: | Re: Polynomialfit Y intercept |
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. |
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