本來在dplyr的函數中是不支持cut函數的（cut為R base函數），但將連續變數依照特定區間分塊貼標籤這使用場景太常見了，要把班上成績，依據80,85,90分別給予C,B,A等操作，且在stackover可以看到非常多類似的問題如下：
Create column with grouped values based on another colum

R dplyr – categorize numeric variable with mutate

Is cut() style binning available in dplyr?

cut function not working in dplyr, but works outside

applying cut within dplyr

cars %>% mutate(type = cut(speed,c(0,15,30),c("slow","fast")))