R/DrawSegment.R

In kmiddleton/kmmisc: KM Misc

#' Draws a line segment of a given slope and intercept only over the
#' range of data present in vector x.
#'
#' @title Draw a line segment
#'
#' @param sl slope of the line
#' @param int intercept of the line
#' @param x vector. x values
#' @param xlog logical. Should x values be logged?
#' @param lty optional parameter for line type
#' @param lwd optional parameter for line width
#'
#' @author Kevin Middleton (\email{middletonk@@missouri.edu})
#'
#' @export
#'
#' @examples
#' set.seed(5)
#' x <- rnorm(20)
#' y <- 2 * x + rnorm(20)
#' fm <- lm(y ~ x)
#'
#' plot(x, y)
#' DrawSegment(coef(fm)[2], coef(fm)[1], x)
DrawSegment <- function(sl,
                        int,
                        x,
                        xlog = FALSE,
                        lty = 1,
                        lwd = 2){
  if (xlog == TRUE) {
      xmin <- min(log10(x))
      xmax <- max(log10(x))
      ymin <- sl * xmin + int
      ymax <- sl * xmax + int
      segments(10 ^ xmin, 10 ^ ymin, 10 ^ xmax, 10 ^ ymax,
               lty = lty, lwd = lwd)
    } else {
    xmin <- min(x)
    xmax <- max(x)
    ymin <- sl * xmin + int
    ymax <- sl * xmax + int
    segments(xmin, ymin, xmax, ymax, lty = lty, lwd = lwd)
  }
}