[NumPy-Tickets] [NumPy] #2208: chebval: subtract half of first coefficient?

NumPy Trac numpy-tickets@scipy....
Mon Aug 27 22:23:50 CDT 2012


#2208: chebval: subtract half of first coefficient?
-------------------------------+--------------------------------------------
 Reporter:  smeared ink        |       Owner:  charris
     Type:  defect             |      Status:  new    
 Priority:  normal             |   Milestone:  1.8.0  
Component:  numpy.polynomial   |     Version:  devel  
 Keywords:  chebyshev chebval  |  
-------------------------------+--------------------------------------------
 I am very new to evaluating Chebyshev polynomials, but shouldn't chebval
 subtract off 0.5*(first coefficient), as in Numerical Recipes, or here?:
 http://mathworld.wolfram.com/ChebyshevApproximationFormula.html (which
 cites Numerical Recipes, actually).

 I was finding unexpected differences in how numpy evaluated Chebyshev
 polynomials from some code I was trying to replicate, and I traced it back
 to this little thing.

-- 
Ticket URL: <http://projects.scipy.org/numpy/ticket/2208>
NumPy <http://projects.scipy.org/numpy>
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