Hi.. I'm relatively new to both nonparametric modeling and R.. I'm trying to fit a regression spline or a piecewise polynomial using R and have teh following qns.:
1. How do I fit a regression spline/piecewise polynomial to the data for some specified degree of the polynomial? 2. How do I obtain the coefficients of the model? I tried the following (based on an example in the help): > data(cars) > attach(cars) > plot(speed, dist, main = "data(cars) & smoothing splines") > cars.spl <- sm.spline(speed, dist) > cars.spl Call: smooth.Pspline(x = ux, y = tmp[, 1], w = tmp[, 2], method = method) Smoothing Parameter (Spar): 366.8429 Equivalent Degrees of Freedom (Df): 2.428851 GCV Criterion: 29.54554 CV Criterion: 39.18787 > coef(cars.spl) NULL As seen above, it doesn't give me the coefficients though it seems to have fitted a piecewise linear model.. I just get "NULL".. is there some other function that will do this? Please cc me on the reply as I'm not subscribed to the list yet.. Thanks, nirmal
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