*! version 1.0.0 93-04-16                 STB-18: sg23
program define diflogen
 version 3.0
*syntax "diflogen: freqvar diflogvar"
 capture confirm variable `1'
 capture confirm new variable `2'
 if _rc~=0 {
      display "syntax: diflogen freqvar diflogvar"
    exit}
 tempvar logfreq laglog
 gen `logfreq'=log(`1')
 gen `laglog'=`logfreq'[_n+1]
 gen `2'=`laglog'-`logfreq'
end