factor is a categorical variable that has different flavors and levels
對因子做表格,查看每個級別的數量
table(reddit$employment.status)
查看因子的所有級別
levels(reddit$age.range)
畫出因子的直方圖圖
qplot(data=reddit,x=age.range)
對因數age.range進行排序
reddit$age.range <- ordered(reddit$age.range,levels=c('Under 18','18-24','25-34','35-44',
'45-54','55-64','65 of Above'))
reddit$age.range <- factor(reddit$age.range,levels=c('Under 18','18-24','25-34','35-44',
'45-54','55-64','65 of Above'),ordered=T)
