Homework Problem 2, STAT 705, Fall 2015.

Assigned 9/2/2015,  Due 9/16/2015


Download the ASCII (text) data-file

http://www.math.umd.edu/~evs/s430.old/Data/nature02801-s2.dat

This is a file of data on Polynesian islands compiled by two
eminent geographers, to investigate which geographic predictors
might account for the degree of deforestation (1:5,  with 5
indicating maximum deforestation) on those islands.

   (a) Create the data-frame "Polynes" consisting only of the
named columns numbered  1:5,7,9:11,15  from the indicated text
data-file by using the "read.table" R function. (The first
column of numbers in the file does not count: those are row
identifiers.) Maintain the column headers as column names.
In your resulting data frame, print the column names together
with their "class" (numeric, integer, character, factor, logical).

   (b) Create and print a vector with entry-names equal to the
data-frame column names, and with numeric entry equal to the
numbner of missing ("NA") values in that column.

   (c) Create and print a matrix with columns corresponding
to all "numeric" or "integer" columns, and with 4 rows containing
respectively the  mean, the standard deviation, the IQR (upper
quartile minus lower quartile), and the range (max minus min) of
all non-missing entries of that column. Your matrix should have
rows and columns named and labelled. Also: you should print no
more than 3 decimal digits in any column.

   (d) Find and print the row-indices in your data-frame of those
successive pairs of "Islnd" names which differ only in their last
letter and for which those last letters are first "L" and then "W".
(Note that "L" stands for Leeward, and "W" for windward side of
the same island.) Find and print the vector of numeric values,
with number of entries equal to the number of these pairs,
consisting of the Rain value for the first member of the pair
(the one ending in "L") minus the Rain value for the second
(the "W") member of the pair.
NOTE: to do this problem part, you will need first to convert the
"Islnd" column from factor to character. We will discuss in class
how to do this.


YOU SHOULD HAND IN THE R CODE TO ACCOMPLISH EACH OF THESE TASKS, 
ALONG WITH THE REQUESTED OUTPUT, A FEW COMMANDS WHOSE OUTPUTS WILL 
VERIFY THAT YOUR CODE PERFORMED THE REQUESTED TASKS, AND NOTHING ELSE.