R/create_sd_polygon.R

In Sumpfohreule/BodenfeuchteGraphen: Plotting of specific soil humidity data of the FVA

#' Creating a sd polygon-table
#'
#' This function creates a table, which can be used to plot a sd-polygon in
#' ggplot etc.
#' @param x A numeric vector with the same length as y
#' @param y A numeric vector with the same length as x
#' @param sd The standard deviation value calculated for the data
#' @return A data frame with the polygon coordinates, which is centered
#' around the \code{y} values with an equal distance of \code{sd}
#' @export
#'
create_sd_polygon <- function(x, y, sd) {
    assertthat::assert_that(length(x) == length(y))
    sd.top <- y + sd
    sd.bot <- y - sd
    data.frame(x = c(x, rev(x)), y = c(sd.bot, rev(sd.top)))
}