Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.



Re: Which interpolation?
Posted:
Dec 7, 2012 3:48 PM


The data presented suggest that the function has a horizontal asymptote at y = 1. If you expect that this is the case, you should try a model that has such an asymptote. E.g., y(x) = 1 + a/x + b/x^2 + ... or y(x) = A*exp(a*x) + B*exp(b*x) + ....
Dave
On Friday, December 7, 2012 12:13:12 PM UTC6, Cristiano wrote: > From a very slow simulation I got y= f(x): > > x y > > 5 0.8048174 > > 6 0.8194384 > > ... > > 44 0.9706268 > > 47 0.9724846 > > ... > > 48765 0.9999756 > > 53765 0.9999776 > > > > For every x, I stop the simulation when the confidence interval for y is > > less than 2,5*10^6 (with 99% of confidence). > > > > I can't calculate all the x's (because the simulation is very slow), so > > I need to interpolate; for example, I don't have y(45) or y(46). > > > > Using the LevenbergMarquardt Least Squares Fitting, the best equation I > > found gives an error that is too high (about 10^4 for small x's). > > > > Then I thought to use a cubic spline, but I notice some "fluctuations" > > on the tails. > > > > Should I use LM or spline? > > > > Thanks > > Cristiano



