11.1 forcats

library(forcats)
library(dplyr)
## 
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
## 
##     filter, lag
## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union
library(ggplot2)

x1 <- c("M", "T", "W", "R", "F", "S", "U")
x2 <- c("Sa", "Su")