e02akf

e02akf © Numerical Algorithms Group, 2002.

Purpose

E02AKF Evaluation of fitted polynomial in one variable, from Chebyshev series form

Synopsis

[result,ifail] = e02akf(xmin,xmax,a,x<,ifail>)

Description

 
 If supplied with the coefficients a , for i=0,1,...,n, of a 
                                    i                       
              _               
 polynomial p(x) of degree n, where
 
                    _   1        _           _
                  p(x)= -a +a T (x)+...+a T (x),
                        2 0  1 1         n n  
 
                                     _                           
 this routine returns the value of p(x) at a user-specified value 
                            _                                   
 of the variable x. Here T (x) denotes the Chebyshev polynomial of
                          j                                     
                                          _                    
 the first kind of degree j with argument x. It is assumed that 
                          _                                     
 the independent variable x in the interval [-1,+1] was obtained 
 from the user's original variable x in the interval [x   ,x   ] 
                                                       min  max 
 by the linear transformation
 
                           2x-(x   +x   )
                        _       max  min 
                        x= --------------.
                             x   -x      
                              max  min

Parameters

e02akf

Required Input Arguments:

xmin                                  real
xmax                                  real
a (:)                                 real
x                                     real

Optional Input Arguments:                       <Default>

ifail                                 integer  -1

Output Arguments:

result                                real
ifail                                 integer