因子（factor）demo2-3.R
数据的类型分为名义型、有序型和连续型
其中名义型和有序型被称为因子
1 > weekdays<-c('Sunday','Monday','February','Wednesday','Thursday','Friday','Saturday') 2 > weekdays 3 [1] "Sunday" "Monday" "February" "Wednesday" "Thursday" "Friday" "Saturday" 4 > weekdays<-factor(weekdays) 5 > weekdays 6 [1] Sunday Monday February Wednesday Thursday Friday Saturday 7 Levels: February Friday Monday Saturday Sunday Thursday Wednesday 8 > #默认因子排序是按照字符排序
可以自己指定因子的顺序
1 > weekdays<-factor( 2 + weekdays, 3 + ordered = T, 4 + levels = c('Sunday','Monday','February','Wednesday','Thursday','Friday','Saturday')) 5 > weekdays 6 [1] Sunday Monday February Wednesday Thursday Friday Saturday 7 Levels: Sunday < Monday < February < Wednesday < Thursday < Friday < Saturday