program define friedman
version 2.1
*! version 1.01   17 July 1991 (now works with > 43 variables
        if "%_*"=="" {
                di in red "invalid syntax -- see help friedman"
                exit 198
        }
        mac def _varlist "req ex min(2)"
        mac def _if "opt"
        mac def _in "opt"
        parse "%_*"
        parse "%_varlist", parse(" ")
         qui count %_if %_in
         mac def _obs=_result(1)
         mac def _sor="%_1"
         while ("%_1"!="") {
              mac def _it=%_it + 1
              genrank r%_it=%_1 %_if %_in
              qui sort %_sor
              qui summ r%_it %_if %_in
              if (_result(1)<%_obs) {
                   di in red "missing values not allowed -- see help friedman"
                   drop r*
                   exit
              }
         mac shift
         }
    genvsum r*, gen(sum_rs)
    gen sum_rssq=sum_rs^2
    qui gen _rsq=cond(_n==_N,sum(sum_rssq),.)
         mac def _k=%_it
         mac def _S=_rsq[_N]-(((%_k^2)*%_obs*(%_obs+1)^2)/4)
         mac def _F=(12*%_S)/(%_k*%_obs*(%_obs+1))
         mac def _W=(12*%_S)/((%_k^2)*%_obs*(%_obs^2-1))
         mac def _prob=%_k*(%_obs-1)*%_W
di "Friedman = "%8.4f %_F
di "Kendall = "%8.4f %_W
di "p-value = "%8.4f chiprob(%_obs-1,%_prob)
drop r* sum_r* _rsq
end