Ты имеешь в виду это?
df<-data.frame(Month = rep(c("January", "February", "March", "April", "May", "June",
"July", "August", "September", "October",
"November", "February", "March"),each = 20),
Year = rep(c("2018", "2019"), times = c(220, 40)),
Type = rep(c("C", "T"), 260),
Value = runif(260, min = 10, max = 55))
df$Month <- factor(df$Month,levels=c("January", "February", "March", "April", "May", "June",
"July", "August", "September", "October",
"November", "Dicember"), ordered = T)
df$Month<-ordered(df$Month)
df$Year<-ordered(df$Year)
df$Year_Month <- paste0(df$Month, " ", df$Year)
df$Year_Month <- factor(df$Year_Month, levels = unique(df$Year_Month))
ggplot(df) +
geom_boxplot(aes(x = Year_Month, y = Value, fill = Type))
![enter image description here](https://i.stack.imgur.com/wQCOo.png)