options ls = 76 ps = 60;
  /* these change line size (ls) and number of lines per page (ps) */
  
data corn;
  infile '/home/pdixon/WWW/stat401b/data/corn.txt';
  input year rain yield;
  rain2 =  rain*rain;
  rain2a =  rain**2;     /* another way to calc. rain squared */
       
proc plot;
  plot yield*rain;
  plot yield*rain = "*" $ year;
    /* the $ year labelling does not work in gplot */
    
proc glm;
  model yield =  rain rain2;
  title 'quadratic regression of yield on rain';

proc glm;
  model yield =  rain rain*rain;
  title 'another way to fit quadratic regression of yield on rain';