Code from class

somefunction <- function (...)
{
  k <- length(ll <- list(...))
  if (k == 0L)
    return(invisible())
  mc <- match.call()
  for (i in 1L:k) if (!(is.logical(r <- ll[[i]]) && !any(is.na(r)) &&
                        all(r))) {
    ch <- deparse(mc[[i + 1]], width.cutoff = 60L)
    if (length(ch) > 1L)
      ch <- paste(ch[1L], "....")
    stop(paste(ch, " is not ", if (length(r) > 1L)
      "all ", "TRUE", sep = ""), call. = FALSE)
  }
  invisible()
}
somefunction(mtcars)

# Your Turn
larger <- function(x, y) {
  y.is.bigger <- y > x
  x[y.is.bigger] <- y[y.is.bigger]
  x
}
larger(c(1, 5, 10), c(2, 4, 11))
larger(c(1, 5, 10), 6)

larger(c(1, 5, 10), c(11, 6))

# Your Turn - Discussion
larger <- function(x, y) {
  len_x <- length(x)
  len_y <- length(y)
  if (len_x != len_y) {
    # warn in case one vector is not a multiple of the other in length
    shortie <- min(len_x, len_y)
    longer <- max(len_x, len_y)
    if (longer %% shortie != 0)
      warning("one vector is not a multiple of the other in length")

    if (len_y < len_x) y <- rep(y, length.out = len_x)
    if (len_x < len_y) x  <- rep(x, length.out = len_y)
  }
  y.is.bigger <- y > x
  x[y.is.bigger] <- y[y.is.bigger]
  x
}


stopifnot(is.character(1:10))


library(assertthat)
assert_that(is.character(1:10))

col_means <- function(df) {
  numeric <- sapply(df, is.numeric)
  numeric_cols <- df[, numeric]

  data.frame(lapply(numeric_cols, mean))
}