Create the data set. CITYTEMP contains the average monthly temperatures of three cities: Raleigh, Minneapolis, and Phoenix.

data citytemp;
   input  month faren city $ @@;
   datalines;
   1      40.5    Raleigh     1      12.2    Minn
   1      52.1    Phoenix     2      42.2    Raleigh
   2      16.5    Minn        2      55.1    Phoenix
   3      49.2    Raleigh     3      28.3    Minn
   3      59.7    Phoenix     4      59.5    Raleigh
   4      45.1    Minn        4      67.7    Phoenix
   5      67.4    Raleigh     5      57.1    Minn
   5      76.3    Phoenix     6      74.4    Raleigh
   6      66.9    Minn        6      84.6    Phoenix
   7      77.5    Raleigh     7      71.9    Minn
   7      91.2    Phoenix     8      76.5    Raleigh
   8      70.2    Minn        8      89.1    Phoenix
   9      70.6    Raleigh     9      60.0    Minn
   9      83.8    Phoenix    10      60.2    Raleigh
  10      50.0    Minn       10      72.2    Phoenix
  11      50.0    Raleigh    11      32.4    Minn
  11      59.8    Phoenix    12      41.2    Raleigh
  12      18.6    Minn       12      52.5    Phoenix
;