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Rick Aster: Professional SAS Programming Shortcuts: Contents

Chapter 48
Program
Data step formulas for descriptive statistics

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data _null_;
   retain;
   set a (keep=a) end=last;
   if missing(a) then nmiss + 1;
   else do;
      n + 1;
      sum + a;
      uss + a*a;
      sc + a*a*a;
      sf + a*a*a*a;
      if min = . then min = a;
      min = min min a;
      max = max max a;
      end;
   if last then do;
      if n >= 1 then do;
         range = max - min;
         mean = sum/n;
         css = uss - mean*sum;
         end;
      if n >= 2 then do;
         var = css/(n - 1);
         std = sqrt(var);
         stderr = sqrt(var/n);
         if mean then cv = 100*std/mean;
         if std then do;
            if n >= 3 then skewness =
                (sc - 3*mean*uss + 2*mean*mean*sum)
                / (var*std) * n/((n - 1)*(n - 2));
            if n >= 4 then kurtosis = (sf - 4*mean*sc 
                + 6*mean*mean*uss - 3*mean*mean*mean*sum)
                / (var*var) * n*(n + 1)/((n - 1)*(n - 2)*(n - 3))
                - 3*(n - 1)*(n - 1)/((n - 2)*(n - 3));
           t = mean/stderr;
           prt = 2*probt(-abs(t), n - 1);
           end;
        end;
     put 'Descriptive Statistics Calculated In A Data Step' //
         n= / nmiss= / min= / max= / range= /
         sum= / mean= / uss= / css= / var= / std= / stderr= /
         cv= / skewness= / kurtosis= / t= / prt= ;
     end;
run;