R/dbbin.R

In dbplot: Simplifies Plotting Data Inside Databases

#' Bin formula
#'
#' Uses the rlang package to build the formula needed to create the bins of a numeric variable
#' in an unevaluated fashion.  This way, the formula can be then passed inside a dplyr
#' verb.
#'
#' @param var Variable name or formula
#' @param bins Number of bins. Defaults to 30.
#' @param binwidth Single value that sets the side of the bins, it overrides bins
#'
#' @examples
#'
#' library(dplyr)
#'
#' # Important: Always name the field and
#' # prefix the function with `!!`` (See Details)
#'
#' # Uses the default 30 bins
#' mtcars %>%
#'   group_by(x = !!db_bin(mpg)) %>%
#'   tally()
#'
#' # Uses binwidth which overrides bins
#' mtcars %>%
#'   group_by(x = !!db_bin(mpg, binwidth = 10)) %>%
#'   tally()
#' @export
db_bin <- function(var, bins = 30, binwidth = NULL) {
  var <- enquo(var)
  var <- quo_squash(var)

  range <- expr((max(!!var, na.rm = TRUE) - min(!!var, na.rm = TRUE)))

  if (is.null(binwidth)) {
    binwidth <- expr((!!range / !!bins))
  } else {
    bins <- expr(as.integer(!!range / !!binwidth))
  }

  bin_number <- expr(as.integer(floor((!!var - min(!!var, na.rm = TRUE)) / !!binwidth)))

  expr(((!!binwidth) *
    ifelse(!!bin_number == !!bins, !!bin_number - 1, !!bin_number)) + min(!!var, na.rm = TRUE))
}

bin_size <- function(.data, field) {
  field <- enquo(field)

  vals <- pull(.data, !!field)
  vals_sort <- sort(vals)
  sort_1 <- vals_sort[1:length(vals_sort) - 1]
  sort_2 <- vals_sort[2:length(vals_sort)]
  comp <- sort_1 - sort_2
  comp <- comp[comp != 0]
  comp <- sort(-comp)
  comp[1]
}