LOCFIT: R and S-Plus Help

locfit(y~x1+cpar(x2))

A term entered in a locfit model formula using cpar will result in a fit that is conditionally parametric. If the formula is y~x1+cpar(x2), the resulting surface, for fixed x1, will be quadratic (using the default deg=2) in x2. Note that the coefficients of the quadratic may depend on x1; this distinguishes a conditionally parametric model from a semiparametric model.

x2

numeric variable.

data(ethanol)
# fit a conditionally parametric model
fit <- locfit(NOx~E+cpar(C),data=ethanol)
plot(fit)
# one way to force a parametric fit with locfit
fit <- locfit(NOx~cpar(E),data=ethanol)

locfit

models