R/MakeBreaks.R

In metR: Tools for Easier Analysis of Meteorological Fields

#' Functions for making breaks
#'
#' Functions that return functions suitable to use as the `breaks` argument in
#' ggplot2's continuous scales and in [geom_contour_fill].
#'
#' @param binwidth width of breaks
#' @param bins number of bins, used if `binwidth = NULL`
#' @param exclude a vector of breaks to exclude
#' @param anchor anchor value
#'
#' @return
#' A function that takes a range as argument and a binwidth as an optional argument
#' and returns a sequence of equally spaced intervals covering the range.
#'
#' @details
#' `MakeBreaks` is essentially an export of the default way
#' [ggplot2::stat_contour] makes breaks.
#'
#' `AnchorBreaks` makes breaks starting from an `anchor` value and covering
#' the range of the data according to `binwidth`.
#'
#' @examples
#'
#' my_breaks <- MakeBreaks(10)
#' my_breaks(c(1, 100))
#' my_breaks(c(1, 100), 20)    # optional new binwidth argument ignored
#'
#' MakeBreaks()(c(1, 100), 20)  # but is not ignored if initial binwidth is NULL
#'
#' # One to one mapping between contours and breaks
#' library(ggplot2)
#' binwidth <- 20
#' ggplot(reshape2::melt(volcano), aes(Var1, Var2, z = value)) +
#'     geom_contour(aes(color = after_stat(level)), binwidth = binwidth) +
#'     scale_color_continuous(breaks = MakeBreaks(binwidth))
#'
#' #Two ways of getting the same contours. Better use the second one.
#' ggplot(reshape2::melt(volcano), aes(Var1, Var2, z = value)) +
#'     geom_contour2(aes(color = after_stat(level)), breaks = AnchorBreaks(132),
#'                   binwidth = binwidth) +
#'     geom_contour2(aes(color = after_stat(level)), breaks = AnchorBreaks(132, binwidth)) +
#'     scale_color_continuous(breaks = AnchorBreaks(132, binwidth))
#'
#' @export
#' @family ggplot2 helpers
MakeBreaks <- function(binwidth = NULL, bins = 10, exclude = NULL) {
    force(binwidth)
    force(bins)
    force(exclude)
    function(range, binwidth2 = NULL) {
        if (!is.null(binwidth)) binwidth2 <- binwidth

        # If no parameters set, use pretty bins
        if (is.null(binwidth2)) {
            b <- pretty(range, bins)
            return(b[!(b %in% exclude)])
        } else {
            b <- scales::fullseq(range, binwidth2)
            b[!(b %in% exclude)]
        }
    }
}

#' @rdname MakeBreaks
#' @export
AnchorBreaks <- function(anchor = 0, binwidth = NULL, exclude = NULL,  bins = 10) {
    force(anchor)
    force(binwidth)
    force(exclude)
    force(bins)
    function(x, binwidth2 = NULL) {
        if (!is.null(binwidth)) binwidth2 <- binwidth
        if (is.null(binwidth2)) {
            binwidth2 <- diff(pretty(x, bins))[1]
        }

        mult <- ceiling((x[1] - anchor)/binwidth2) - 1L
        start <- anchor + mult*binwidth2
        b <- seq(start, x[2] + binwidth2, binwidth2)
        b[!(b %in% exclude)]
    }
}


# InScale <- function(fun, binwidith, ...) {
#     function(range){
#         fun(range, binwidth, ...)
#     }
# }
#
# InContour <- function(fun, ...) {
#     function(range, binwidth) {
#         fun(range, ...)
#     }
# }