   a table with three varialbe:treatment
(low,high),size(large,small),response y
  I want all response y with treatment=low and size=large,
  I try to write as :
treatment<-c("low","low","high","high")
size<-c("small","large","small","large")
y<-c(1,2,4,5)
table1<-data.frame(treatment,size,y)
x=table1$y(treatment=="low"& size=="large")

this does not work out~

thank you for the help~

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