A loggr example

loggrex.R

library(loggr) # should be executed before sourcing the script

log_file("all.log")
log_file("messages.log", DEBUG, INFO, .warning = FALSE, .error = FALSE)
log_file("console", WARN, ERROR, CRITICAL, .message = FALSE)

top_n <- function(data_set, sort_var, n = 3, desc = FALSE)
{
  if (!is.data.frame(data_set))
    log_critical("Invalid data_set provided.")

  if (!is.character(sort_var) || !sort_var %in% names(data_set))
    log_critical("Invalid column for sorting.")

  if (NROW(data_set) < n) {
    log_warn("Not enough rows in data set. Returning all rows.")
    return(data_set)
  }

  msg <- sprintf("Received %d rows. Selecting top %d according to %s (%s).",
                 NROW(data_set),
                 n,
                 sort_var,
                 if (desc) "descending" else "ascending")

  log_info(msg)

  idx <- order(data_set[[sort_var]], decreasing = desc)
  head(data_set[idx, ], n)
}

top_n(iris, "Sepal.Width", 3)
top_n(iris, "Sepal.Width", 3, desc = TRUE)
top_n(iris[1:3, ], "Sepal.Width", 5)
top_n(1:10, "nosuch", 5)