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background_polynomial [2011/08/25 07:31]
alancoelho
background_polynomial [2011/08/25 19:12]
alancoelho
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 Chebyshev polynomials of the first kind as described at http://​mathworld.wolfram.com/​ChebyshevPolynomialoftheFirstKind.html is used by default in Topas. The recurrences relations of Eq. (26) can be used with the x axis normalized to be between -1 and 1.  Chebyshev polynomials of the first kind as described at http://​mathworld.wolfram.com/​ChebyshevPolynomialoftheFirstKind.html is used by default in Topas. The recurrences relations of Eq. (26) can be used with the x axis normalized to be between -1 and 1. 
  
-A Chebychev Polynomial, say order 5, written as a fit_obj ​can be coded as:+A Chebychev Polynomial, say order 5, written as
 + 
 +<code topas>​bkg @  359.793901` ​ 140.27403` ​ 67.3210027` ​ 21.057843` ​ 11.3443248` -4.46398819`</​code>​ 
 + 
 +can be coded as a fit_obj as follows:
  
 <code topas>​prm c0  359.79390` <code topas>​prm c0  359.79390`
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 Note that X1 and X2 are reserved parameter names that correspond to the start and end of the x-axis. Note that X1 and X2 are reserved parameter names that correspond to the start and end of the x-axis.
  
-The attached AAC.INP and data file demonstrates that the fit_obj coefficients after refinement corresponds exactly to those of the bkg Chebychev Polynomial.+ --- //[[alan.coelho@bigpond.com|Alan Coelho]] 2011/08/25 19:12//
  

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