R/month-scale.R

In grates: Grouped Date Classes

grates_month_env <-  new.env(parent = emptyenv())

# -------------------------------------------------------------------------
#' Month scale
#'
# -------------------------------------------------------------------------
#' ggplot2 scale for a month vector.
#'
# -------------------------------------------------------------------------
#' @param breaks
#'
#' A `<grates_month>` vector of the desired breaks.
#'
#' @param n.breaks `[integer]`
#'
#' Approximate number of breaks calculated using `scales::breaks_pretty`
#' (default 6L).
#'
#' Will only have an effect if `breaks = waiver()`.
#'
#' @param format
#'
#' Format to use if "Date" scales are required.
#'
#' If NULL then labels are centralised and of the form "lower category bound to
#' upper category bound".
#'
#' If not NULL then the value is used by `format.Date()` and can be any input
#' acceptable by that function (defaults to "%Y-%m-%d).
#'
#' @param bounds_format
#'
#' Format to use for grouped date labels. Only used if `format` is NULL.
#'
#' @param sep `[character]`
#'
#' Separator to use for grouped date labels.
#'
#' @param n `[integer]`
#'
#' Number of months used for the original grouping.
#'
#' @param ...
#'
#' Not currently used.
#'
# -------------------------------------------------------------------------
#' @return
#' A scale for use with ggplot2.
#'
# -------------------------------------------------------------------------
#' @examplesIf requireNamespace("outbreaks") && requireNamespace("ggplot2")
#'
#' # use simulated linelist data from the outbreaks package
#' linelist <- outbreaks::ebola_sim_clean$linelist
#'
#' # calculate the bimonthly number of cases
#' x <- as_month(linelist$date_of_infection, n = 2)
#' (dat <- aggregate(list(cases = x), by = list(group = x), FUN = length))
#'
#' # by default lower date bounds are used for the x axis
#' (bimonth_plot <-
#'     ggplot2::ggplot(dat, ggplot2::aes(group, cases)) +
#'     ggplot2::geom_col(width = 1, colour = "white") +
#'     ggplot2::theme_bw() +
#'     ggplot2::theme(
#'         axis.text.x = ggplot2::element_text(
#'             angle = 45,
#'             hjust = 1
#'         )
#'     ) +
#'     ggplot2::xlab(""))
#'
#' # To obtain centred labels you must explicitly set the format to NULL
#' # in the scale:
#' bimonth_plot + scale_x_grates_month(format = NULL, n = 2)
#'
# -------------------------------------------------------------------------
#' @export
scale_x_grates_month <- function(
    ...,
    breaks = ggplot2::waiver(),
    n.breaks = 6L,
    format = "%Y-%m-%d",
    bounds_format = "%Y-%b",
    sep = "to",
    n
) {

    .check_suggests("ggplot2")
    .check_suggests("scales") # precautionary but overkill as currently a dependency of ggplot2

    if (missing(n))
        n <- grates_month_env$n

    if (is.null(n))
        stop("Please specify the `n` of the grate_month input")

    if (!is.integer(n)) {
        if (!.is_whole(n))
            stop("`n` must be an integer of length 1.")
        n <- as.integer(n)
    }
    if (n <= 1L)
        stop("`n` must be greater than 1. Did you mean to call scale_x_grates_yearmonth?")

    # set environment variables to NULL so they don't mess other plots up
    grates_month_env$n <- NULL

    # ggplot2 3.5.0 deprecated the `trans` argument in favour of `transform`.
    # We could just force a minimum ggplot2 version and avoid this branching
    # but it's relatively low effort so leaving for now.
    # TODO - revisit.
    if (utils::packageVersion("ggplot2") < '3.5.0') {
        ggplot2::scale_x_continuous(
            trans = .grates_month_trans(
                breaks = breaks,
                n.breaks = n.breaks,
                format = format,
                bounds_format = bounds_format,
                sep = sep,
                n = n
            )
        )
    } else {
        ggplot2::scale_x_continuous(
            transform = .grates_month_trans(
                breaks = breaks,
                n.breaks = n.breaks,
                format = format,
                bounds_format = bounds_format,
                sep = sep,
                n = n
            )
        )
    }

}

# ------------------------------------------------------------------------- #
#' @exportS3Method ggplot2::scale_type
scale_type.grates_month <- function(x) {

    # -------------------------------------------------------------------------
    # -------------------------------------------------------------------------
    # TODO - remove this if https://github.com/tidyverse/ggplot2/issues/4705
    #        gets resolved
    if (!"grates" %in% .packages())
        stop("<grates_month> object found, but grates package is not attached.\n  Please attach via `library(grates)`.")
    # -------------------------------------------------------------------------
    # -------------------------------------------------------------------------

    grates_month_env$n <- attr(x, "n")
    "grates_month"
}

# ------------------------------------------------------------------------- #
# ------------------------------------------------------------------------- #
# -------------------------------- INTERNALS ------------------------------ #
# ------------------------------------------------------------------------- #
# ------------------------------------------------------------------------- #
.grates_month_trans <- function(breaks, n.breaks, format, bounds_format, sep, n) {

    shift <- if (is.null(format)) 0 else 0.5

    # breaks function
    brks <- function(x) {
        if (inherits(breaks, "waiver")) {
            dat <- scales::breaks_pretty(n.breaks)(as.numeric(x))
            dat <- as.integer(floor(dat))
            dat <- as.numeric(new_month(dat, n = n))
        } else {
            dat <- as.numeric(breaks)
        }
        dat - shift
    }

    # format function
    fmt <- function(x) {
        x <- new_month(x + shift, n)
        if (is.null(format)) {
            format.grates_month(x, format = bounds_format, sep = sep)
        } else {
            x <- as.Date.grates_month(x)
            format(x, format)
        }
    }

    scales::trans_new(
        "grates_month",
        transform = as.numeric,
        inverse = as.numeric,
        breaks = brks,
        format = fmt
    )
}