pass column name in data.table using variable in a for loop in R -

i want loop through selection of columns data table , summarise data column. i'm able pass column name in variable using quote() , eval() , works fine

library("data.table")  dt <- data.table(x=c("b","b","b","a","a","c","c"), y = c("x","y","z","x","y","z","x"), v=rnorm(7))  splitby <- quote(y)  sdt <- dt[,list(meanv = mean(v)),by=. (eval(splitby))] 

however when try put loop this

library("data.table")  dt <- data.table(x=c("b","b","b","a","a","c","c"), y = c("x","y","z","x","y","z","x"), v=rnorm(7))  mylist <- c("x","y")  (i in mylist){    splitby <- quote(i)   sdt <- dt[,list(meanv = mean(v)),by=. (eval(splitby))]  } 

it doesn't work. know split evaluates correctly x or y. doing wrong?