library(data.table)
my.dt <- data.table(a=c("$","€","+",0,1,"a","A"))
my.dt[base::order(a)]
#    a
#1: $
#2: €
#3: +
#4: 0
#5: 1
#6: a
#7: A

my.dt[order(a)]
#    a
#1: $
#2: +
#3: 0
#4: 1
#5: A
#6: a
#7: €