Homework No.2 (Due date: March 9th)
[Remark: Throughout the class, our homeworks will (mostly) have different assignments for R and SAS. You have the choice to do one set of assignments (R or SAS) or do both sets (both R and SAS). If you do both sets, the homework score will be calculated by: max(R assigmnet score, SAS assignment score) + a separate bonus score of 10 points. ] 
Problem 1:  For the data set ("animals.dat") which contains body weights and brain weights of 27 species.

                 i) Use [a] read.table() and [b] data.frame()/scan() functions to read the data into R. 

                ii) Produce a scatter plot (with the fitted regression line).
                iii) Fit a linear regression model to the data and report your findings.
                iv) Provide appropriate diagnostic analysis.

Problem 2:  Write your own R function to compute DFFITS, and test it on the "animals.dat" studied in Problem 1.  (Please include your R code -- try your best to make the code concise).

Problem 3: The Janka hardness data gives the density (Dens) and hardness (Hard) of a sample of Australian Eucalypt hardwoods. The problem is to build a prediction equation for hardness in terms of density. ( See dataset junka here. )

Problem 1:  page 135-136, 5-1 and 5-5

Problem 2:  page 136, 5-6

Problem 3:  page 178, 7-2

problem 4:  page 247, 9-1. Also, provide appropriate diagnostic analysis.