ST 555 -- Summer 2013

  Homework #4 -- Due FRIDAY, 14 June 2013

  The file 'kumsio.co2' holds measurements of atmospheric carbon dioxide 
  from the weather station at Cape Kumuhahi in Hawaii.  The header (16 
  lines) describes the source of the data.  The first (partial) year is  
  1979 and the final year is 2007.  Following the data is also a footer.  

  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.)

  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