25.5 Using the rescale01() function

rescale01 <- function(x) {
  (x - min(x, na.rm = TRUE)) / (max(x, na.rm = TRUE) - min(x, na.rm = TRUE))
}

rescale01(c(-10, 0, 10))

## [1] 0.0 0.5 1.0

rescale01(c(1, 2, 3, NA, 5))

## [1] 0.00 0.25 0.50   NA 1.00