R/dlsegments.R

In openintro: Data Sets and Supplemental Functions from 'OpenIntro' Textbooks and Labs

#' Create a Double Line Segment Plot
#'
#' Creae a plot showing two line segments. The union or intersection of those
#' line segments can also be generated by utilizing the \code{type} argument.
#'
#'
#' @param x1 The endpoints of the first interval. Values larger (smaller) than
#' 999 (-999) will be interpreted as (negative) infinity.
#' @param x2 The endpoints of the second interval. Values larger (smaller) than
#' 999 (-999) will be interpreted as (negative) infinity.
#' @param l A vector of length 2, where the values correspond to the left end
#' point of each interval. A value of \code{"o"} indicates the interval is open
#' at the left and \code{"c"} indicates the interval is closed at this end.
#' @param r A vector of length 2, where the values correspond to the right end
#' point of each interval. A value of \code{"o"} indicates the interval is open
#' at the right and \code{"c"} indicates the interval is closed at this end.
#' @param type By default, no intersection or union of the two lines will be
#' shown (value of \code{"n"}). To show the union of the line segments, specify
#' \code{"u"}. To indicate that the intersection be shown, specify \code{"i"}.
#' @param COL If the union or intersection is to be shown (see the \code{type}
#' argument), then this parameter controls the color that will be shown.
#' @param lwd If the union or intersection is to be shown (see the \code{type}
#' argument), then this parameter controls the width of any corresponding lines
#' or open points in the union or intersection.
#' @param ylim A vector of length 2 specifying the vertical plotting limits,
#' which may be useful for fine-tuning plots. The default is \code{c(-0.35,2)}.
#' @param mar A vector of length 4 that represent the plotting margins.
#' @param hideOrig An optional argument that to specify that the two line
#' segments should be shown (\code{hideOrig} takes value \code{FALSE}, the
#' default) or that they should be hidden (\code{hideOrig} takes value
#' \code{TRUE}.
#' @author David Diez
#' @seealso \code{\link{lsegments}}, \code{\link{CCP}},
#' \code{\link{ArrowLines}}
#' @keywords Line Segment Algebra
#' @export
#' @examples
#'
#' dlsegments(c(-3, 3), c(1, 1000),
#'   r = c("o", "o"), l = c("c", "o"), COL = COL[4]
#' )
#'
#' dlsegments(c(-3, 3), c(1, 1000),
#'   r = c("o", "o"), l = c("c", "o"), type = "un", COL = COL[4]
#' )
#'
#' dlsegments(c(-3, 3), c(1, 1000),
#'   r = c("o", "o"), l = c("c", "o"), type = "in", COL = COL[4]
#' )
dlsegments <-
  function(x1 = c(3, 7), x2 = c(5, 9), l = c("o", "o"), r = c("c", "c"), type = c("n", "u", "i"), COL = 2, lwd = 2.224, ylim = c(-0.35, 2), mar = rep(0, 4), hideOrig = FALSE) {
    # x1=c(-1,4); x2=c(3,1000);type="inter"

    type <- type[1]

    if (x1[1] == x1[2] && (l[1] != "c" || r[1] != "c")) {
      warning("'x1' is open, changing to closed")
      l[1] <- "c"
      r[1] <- "c"
    }

    if (x2[1] == x2[2] && (l[2] != "c" || r[2] != "c")) {
      warning("'x2' is open, changing to closed")
      l[2] <- "c"
      r[2] <- "c"
    }

    x1 <- sort(x1)
    x2 <- sort(x2)
    xR <- range(
      x1[x1 > -1000 & x1 < 1000],
      x2[x2 > -1000 & x2 < 1000]
    )
    L <- ifelse(x1[1] < -999 || x2[1] < -999, 0.4, 0.15)
    R <- ifelse(x1[2] > 999 || x2[2] > 999, 0.4, 0.15)
    xlim <- xR + c(-L, R) * diff(xR)
    if (xlim[1] == xlim[2]) {
      xlim[1] <- round(xlim[1] - 3.25)
      xlim[2] <- round(xlim[2] + 3.25)
    }
    graphics::par(mar = mar)
    graphics::plot(1e5, xlim = xlim, ylim = ylim, axes = FALSE, type = "n")
    x1[1] <- ifelse(x1[1] < -999, xlim[1], x1[1])
    x1[2] <- ifelse(x1[2] > 999, xlim[2], x1[2])
    x2[1] <- ifelse(x2[1] < -999, xlim[1], x2[1])
    x2[2] <- ifelse(x2[2] > 999, xlim[2], x2[2])

    # ___ Line 1 ___#
    code1 <- ifelse(x1[1] == xlim[1] && x1[2] == xlim[2], 3,
      ifelse(x1[1] == xlim[1], 1,
        ifelse(x1[2] == xlim[2], 2, 0)
      )
    )
    if (!hideOrig) {
      if (code1 > 0) {
        graphics::arrows(x1[1], 1.1082, x1[2], 1.1082,
          length = 0.07, code = code1, lwd = 0.592
        )
      } else {
        lines(x1, rep(1.1082, 2), lwd = 0.592)
      }
      if (x1[1] > xlim[1]) {
        graphics::points(x1[1], 1.1082, pch = 19, col = "#FFFFFF")
        graphics::points(x1[1], 1.1082, pch = ifelse(l[1] == "c", 19, 1))
      }
      if (x1[2] < xlim[2]) {
        graphics::points(x1[2], 1.1082, pch = 19, col = "#FFFFFF")
        graphics::points(x1[2], 1.1082, pch = ifelse(r[1] == "c", 19, 1))
      }
    }

    # ___ Line 2 ___#
    code2 <- ifelse(x2[1] == xlim[1] && x2[2] == xlim[2], 3,
      ifelse(x2[1] == xlim[1], 1,
        ifelse(x2[2] == xlim[2], 2, 0)
      )
    )
    if (!hideOrig) {
      if (code2 > 0) {
        graphics::arrows(x2[1], 1.729, x2[2], 1.729,
          length = 0.07, code = code2, lwd = 0.592
        )
      } else {
        graphics::lines(x2, rep(1.729, 2), lwd = 0.592)
      }
      if (x2[1] > xlim[1]) {
        graphics::points(x2[1], 1.729, pch = 19, col = "#FFFFFF")
        graphics::points(x2[1], 1.729, pch = ifelse(l[2] == "c", 19, 1))
      }
      if (x2[2] < xlim[2]) {
        graphics::points(x2[2], 1.729, pch = 19, col = "#FFFFFF")
        graphics::points(x2[2], 1.729, pch = ifelse(r[2] == "c", 19, 1))
      }
    }

    # ___ Build Axis ___#
    graphics::arrows(xlim[1], 0.55012, xlim[2], 0.55012,
      length = 0.07, code = 3, lwd = 0.592
    )
    if (TRUE) { # (ticks) {
      if (diff(xlim) < 11) {
        xs <- round(xlim[1]):round(xlim[2])
        if (abs(xs[1] - xlim[1]) < diff(xlim) / 20) {
          xs <- utils::tail(xs, -1)
        }
        if (abs(utils::tail(xs, 1) - xlim[2]) < diff(xlim) / 20) {
          xs <- utils::head(xs, -1)
        }
      } else {
        xs <- union(x1, x2)
        xs <- xs[!xs %in% xlim]
      }
      if (length(xs) > 0) {
        y1 <- rep(0.45, length(xs))
        y2 <- y1 + 0.2
        graphics::segments(xs, y1, xs, y2)
        graphics::text(xs, (y1 + y2) / 2, xs, pos = 1)
      }
    }

    # ___ Intersection ___#
    if (tolower(substr(type, 1, 1)) == "i") {

      # ___ x1 < x2 ___#
      left <- max(x1[1], x2[1])
      right <- min(x1[2], x2[2])
      if (left < right) {
        pch <- c(2, 2)
        pch[1] <- ifelse(x1[1] > x2[1], l[1], l[2])
        if (x1[1] == x2[1]) {
          pch[1] <- ifelse(all(l == "c"), "c", "o")
        }
        pch[2] <- ifelse(x1[2] < x2[2], r[1], r[2])
        if (x1[2] == x2[2]) {
          pch[2] <- ifelse(all(r == "c"), "c", "o")
        }
        pch <- ifelse(pch == "o", 1, 19)
        graphics::lines(c(left, right), rep(0.55012, 2),
          lwd = lwd, col = COL[1]
        )
        graphics::points(c(left, right), rep(0.55012, 2),
          pch = 19, col = "#FFFFFF"
        )
        graphics::points(c(left, right), rep(0.55012, 2),
          pch = pch, col = COL[1]
        )
      } else if (left == right) {

        # ___ Intersection Is Point ___#
        pch1 <- ifelse(x1[1] < x2[1], l[2], l[1])
        pch2 <- ifelse(x1[2] < x2[2], r[1], r[2])
        if (pch1 == "c" && pch[2] == "c") {
          X <- ifelse(x1[1] < x2[1], x2[1], x1[1])
          graphics::points(X, 0.55012, pch = 19, col = COL[1])
        }
      }
    }

    # ___ Union ___#
    if (tolower(substr(type, 1, 1)) == "u") {
      if (code1 > 0) {
        graphics::arrows(x1[1], 0.55012, x1[2], 0.55012,
          length = 0.07, code = code1, lwd = lwd, col = COL[1]
        )
      } else {
        lines(x1, rep(0.55012, 2), lwd = lwd, col = COL[1])
      }

      if (code2 > 0) {
        graphics::arrows(x2[1], 0.55012, x2[2], 0.55012,
          length = 0.07, code = code2, lwd = lwd, col = COL[1]
        )
      } else {
        lines(x2, rep(0.55012, 2), lwd = lwd, col = COL[1])
      }

      X <- c()
      pch <- c()

      # ___ Left Point ___#
      if (x1[1] > xlim[1] && x2[1] > xlim[1]) {
        cond <- x1[1] < x2[1]
        X <- append(X, ifelse(cond, x1[1], x2[1]))
        pch <- append(pch, ifelse(cond, l[1], l[2]))
      }

      # ___ Right Point ___#
      if (x1[2] < xlim[2] && x2[2] < xlim[2]) {
        cond <- x1[2] > x2[2]
        X <- append(X, ifelse(cond, x1[2], x2[2]))
        pch <- append(pch, ifelse(cond, r[1], r[2]))
      }

      # ___ Middle Point 1 ___#
      if (x1[2] < x2[1]) {
        X <- append(X, x1[2])
        pch <- append(pch, r[1])
        X <- append(X, x2[1])
        pch <- append(pch, l[2])
      } else if (x1[2] == x2[1] && r[1] == "o" && l[2] == "o") {
        X <- append(X, x1[2])
        pch <- append(pch, "o")
      }

      # ___ Middle Point 2 ___#
      if (x1[1] > x2[2]) {
        X <- append(X, x1[1])
        pch <- append(pch, l[1])
        X <- append(X, x2[2])
        pch <- append(pch, r[2])
      } else if (x1[1] == x2[2] && r[2] == "o" && l[1] == "o") {
        X <- append(X, x1[1])
        pch <- append(pch, "o")
      }

      # ___ Add Points ___#
      pch <- ifelse(pch == "o", 1, 19)
      graphics::points(X, rep(0.55012, length(X)), pch = 19, col = "#FFFFFF")
      graphics::points(X, rep(0.55012, length(X)), pch = pch, col = COL[1])
    }
  }