Home Manual Packages Global Index Keywords Quick Reference | # functions in fitrat.i - f
fitpol |
                 yp= fitpol(y, x, xp)

           -or- yp= fitpol(y, x, xp, keep=1)
         is an interpolation routine similar to interp, except that fitpol
         returns the polynomial of degree numberof(X)-1 which passes through
         the given points (X,Y), evaluated at the requested points XP.
         The X must either increase or decrease monotonically.
         If the KEEP keyword is present and non-zero, the external variable
         yperr will contain a list of error estimates for the returned values
         yp on exit.
         The algorithm is taken from Numerical Recipes (Press, et. al.,
         Cambridge University Press, 1988); it is called Neville's algorithm.
         The rational function interpolator fitrat is better for "typical"
         functions.  The Yorick implementaion requires numberof(X)*numberof(XP)
         temporary arrays, so the X and Y arrays should be reasonably small.

    interpreted function, defined at i/fitrat.i   line 10
SEE ALSO: | fitrat, interp
fitrat |
                 yp= fitrat(y, x, xp)

           -or- yp= fitrat(y, x, xp, keep=1)
         is an interpolation routine similar to interp, except that fitpol
         returns the diagonal rational function of degree numberof(X)-1 which
         passes through the given points (X,Y), evaluated at the requested
         points XP.  (The numerator and denominator polynomials have equal
         degree, or the denominator has one larger degree.)
         The X must either increase or decrease monotonically.  Also, this
         algorithm works by recursion, fitting successively to consecutive
         pairs of points, then consecutive triples, and so forth.
         If there is a pole in any of these fits to subsets, the algorithm
         fails even though the rational function for the final fit is non-
         singular.  In particular, if any of the Y values is zero, the
         algorithm fails, and you should be very wary of lists for which
         Y changes sign.  Note that if numberof(X) is even, the rational
         function is Y-translation invariant, while numberof(X) odd generally
         results in a non-translatable fit (because it decays to y=0).
         If the KEEP keyword is present and non-zero, the external variable
         yperr will contain a list of error estimates for the returned values
         yp on exit.
         The algorithm is taken from Numerical Recipes (Press, et. al.,
         Cambridge University Press, 1988); it is called the Bulirsch-Stoer
         algorithm.  The Yorick implementaion requires numberof(X)*numberof(XP)
         temporary arrays, so the X and Y arrays should be reasonably small.

    interpreted function, defined at i/fitrat.i   line 72
SEE ALSO: | fitpol, interp