MARS assignment

1) Install and load the mda package

   If you do not have write permission to the R directory, but can write to 
   directory D:/ (say), then use the following commands:

   install.packages("mda", lib="D:/", repos="http://cran.ms.unimelb.edu.au")
   library("mda", lib="D:/")

2) Download ozone.txt from the course web site, then load it using 

   ozone <- read.table("ozone.txt", header=T)
   
   Information on the data set is given in ozone.info
   
3) Fit a MARS model to the ozone data using the mars function

4) Answer the following questions (using the default parameter 
   settings):
   a) Which basis functions appear in the final model?
   b) What is the gcv of the final model, and hence what is the
      sum of squared residuals?
   c) What are the effects of changing the parameters 
      penalty and thresh?
   d) Which basis functions appear in the final model if
      we put degree = 2

5) Show that the function (2 - x)_+ can be written as a linear
   combination of 1, (1 - x)_+, (x - 1)_+ and (x - 2)_+