ST 445 -- Summer 2013

  Homework #4 -- Due MONDAY, 10 June 2013

  Measurements of atmospheric carbon dioxide are in nine files in the 
  directory 'csiro' according to nine stations.  All of these files 
  have a long descriptive header, but the lengths vary.  Below is the 
  list of stations, file names, and the length of the header.  
   Alert              alt_mm.dat        16    
   Cape Ferguson      cferg_mm.dat      16
   Cape Grim          cgrim_mm.dat      16
   Estevan Point      estpo_mm.dat      17
   Macquarie Island   macq_mm.dat       16
   Mawson             mawson_mm.dat     16
   Mauna Loa          mlo_mm.dat        16
   Shetland Islands   shetland_mm.dat   16
   South Pole         spo_mm.dat        16

  All stations end in 2001, except for Alert which ends in 2006.

  For more information about these data, see
    http://cdiac.ornl.gov/trends/co2/csiro
  These files all have the following format: a header, then the data, 
  then a footer with more explanatory information.  The body of the 
  data has a column for the year, then twelve columns of monthly values,
  and the annual average column for a total of 14 columns.  These values
  are *tab-delimited* so use 'dsd' and 'dlm' in your infile statement.

  Read in the data from one station and perform the following tasks:

 a) Create a dataset with each observation corresponding to a month, 
 with variables YEAR, MONTH (numeric), and CO2.  Also create a time or
 date variable that properly indexes the data.

 b) Plot CO2 versus time/date.

 c) Check whether given the annual averages match (close enough) the 
 sample mean from the monthly values.  (Note the given annual average 
 is missing for a year if any monthly value is missing.)

 d) What month has the highest average carbon dioxide?

 e) Using a simple linear regression model with year and annual averages,
 estimate the annual rate of change (slope) (and give a standard error).
  (You may want to create a different dataset to do this part.)

  Which station to read?  Use the last digit of your student id and take
  the stations in numeric order: Alert (1), Cape Ferguson (2), ..., 
  South Pole (9).  If you have a 0 in your student id, use the last 
  nonzero digit.

  FOR ALL EXERCISES: Hand in (paper) (1) The answers to any questions 
  asked. (2) Your program * With at least as many comments as you have 
  toes! * (3) Your output