library(vioplot)
x1 = mtcars$mpg[mtcars$cyl==4]
x2 = mtcars$mpg[mtcars$cyl==6]
x3 = mtcars$mpg[mtcars$cyl==8]
xdata = paste("x1","x2","x3",sep=",") # Try 1
xdata = c("x1","x2","x3")             # Try 2
vioplot(xdata, names=c("4 cyl", "6 cyl", "8 cyl"),col="grey")

library("vioplot")
x1 <- mtcars$mpg[mtcars$cyl==4]
x2 <- mtcars$mpg[mtcars$cyl==6]
x3 <- mtcars$mpg[mtcars$cyl==8]

xdata <- list(x1, x2, x3, names=c("4 cyl", "6 cyl", "8 cyl"), col="grey")
do.call(vioplot, xdata)

cyls <- c(4, 6, 8)
cyldata <- lapply(cyls, function(cyl) mtcars$mpg[mtcars$cyl == cyl])
xdata <- c(cyldata, list(names=paste(cyls, "cyl"), col="grey"))
do.call(vioplot, xdata)

vioplot(x1,x2,x3, names=c("4 cyl", "6 cyl", "8 cyl"),col="grey")

params <- list("Hello World", 2, 5)
do.call(substr, params)
>> "ello"

params <- list(2, 5)
do.call(substr, c("Hello World", params))
>> "ello"

params <- list(stop=5, x="Hello World", start=2)
do.call(substr, params)
>> "ello"

params <- list("Hello World", start=2, stop=5)
do.call(substr, params)
>> "ello"

make_substr <- function(start, stop){
  return(
    function(string) {
      substr(string, start, stop)
    }
  )
}
substr_2_5 <- make_substr(2, 5)

substr_2_5("Hello World")
>> "ello"
substr_2_5("Goodbye")
>> "oodb"