base-mutate.R

data(diamonds, package = "ggplot2")

# Most straightforward
diamonds$ppc <- diamonds$price / diamonds$carat

# Avoid repeating diamonds 
diamonds$ppc <- with(diamonds, price / carat)

# The inspiration for dplyr's mutate
diamonds <- transform(diamonds, ppc = price / carat)
diamonds <- diamonds |> transform(ppc = price / carat)

# Similar to transform(), but uses assignment rather argument matching
# (can also use = here, since = is equivalent to <- outside of a function call)
diamonds <- within(diamonds, {
  ppc <- price / carat
})
diamonds <- diamonds |> within({
  ppc <- price / carat
})

# Protect against partial matching
diamonds$ppc <- diamonds[["price"]] / diamonds[["carat"]]
diamonds$ppc <- diamonds[, "price"] / diamonds[, "carat"]

# FORBIDDEN
attach(diamonds)
diamonds$ppc <- price / carat