- How to choose the
`span`

parameter?
- Which model is the best? Why?

obj3 <- loess(logratio ~ range, data = lidar.train, span = 1,
control = loess.control(surface = 'direct'))
obj2 <- loess(logratio ~ range, data = lidar.train, span = .3,
control = loess.control(surface = 'direct'))
obj1 <- loess(logratio ~ range, data = lidar.train, span = .02,
control = loess.control(surface = 'direct'))

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : span too small. fewer data values than degrees of freedom.

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : pseudoinverse used at 390

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : neighborhood radius 3

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : reciprocal condition number 0

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : There are other near singularities as well. 4

## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : Chernobyl! trL>n 198
## Warning in simpleLoess(y, x, w, span, degree = degree, parametric =
## parametric, : Chernobyl! trL>n 198

## Warning in sqrt(sum.squares/one.delta): NaNs produced