Sticky-note

The METROPOP data set contains one variable, Populationcount, with the metropolitan and nonmetropolitan population counts. DECADE indicates the census year for the observation. The OUTPUT statements create two observations for each state and decade combination.

data metropop;
   set statepop;
   keep Region Decade Populationcount;
   label PopulationCount='US Census Population (millions)'
         Decade='Census year';
   decade=1980;
   populationcount=sum(citypop_80,noncitypop_80);
   output;
   decade=1990;
   populationcount=sum(citypop_90,noncitypop_90);
   output;