library(openxlsx)

df<-read.xlsx("http://kanggc.iptime.org/book/data/finance-k.xlsx")
df_dat<-data.matrix(df)

year<-df_dat[,1]
jj<-df_dat[,18]
jj

bins<-c(22,26,30,34,38,42)
bins

class<-cut(jj,breaks=bins)
class

table(class)
transform(table(class),Rel_Freq=prop.table(Freq))

hist(jj, breaks=bins, xlim=c(22,42))