In R, how do I compute factors' percentage given on different variable? [duplicate]

Answer 1

You could modify your ddply code to:

 ddply(data,.(State), 
    function(x) with(x,
      data.frame(100*round(table(Ideology)/length(Ideology),2))))

 #    State     Ideology Freq
 #1    CO Conservative   33
 #2    CO  Independent   17
 #3    CO      Liberal   50
 #4    DC Conservative   33
 #5    DC  Independent   33
 #6    DC      Liberal   33