I am not 100% certain, but I think this does what you want using prop.table. See mostly the last 3 lines. The rest of the code is just creating fake data.
set.seed(1234)
total_bill <- rnorm(50, 25, 3)
tip <- 0.15 * total_bill + rnorm(50, 0, 1)
sex <- rbinom(50, 1, 0.5)
smoker <- rbinom(50, 1, 0.3)
day <- ceiling(runif(50, 0,7))
time <- ceiling(runif(50, 0,3))
size <- 1 + rpois(50, 2)
my.data <- as.data.frame(cbind(total_bill, tip, sex, smoker, day, time, size))
my.data
my.table <- table(my.data$smoker)
my.prop <- prop.table(my.table)
cbind(my.table, my.prop)