R/geoCartesianSegmentLocator.R

In lindbrook/cholera: Amend, Augment and Aid Analysis of John Snow's Cholera Map

#' Locate road by name on geo-cartesian map.
#'
#' @param street.name Character. Vector of street names.
#' @param zoom Logical or Numeric. Numeric unit in "meters".
#' @param street.col Character. Color of streets.
#' @return A base R graphics plot.
#' @noRd

geoCartesianStreetLocator <- function(street.name = NULL, zoom = TRUE,
  street.col = "gray") {

  real.road.names <- streetNames()

  if (!is.null(street.name)) {
    st.nm <- vapply(street.name, caseAndSpace, character(1L))
    if (all(st.nm %in% real.road.names == FALSE)) {
      error.msg <- "Invalid street name(s). See streetNames()."
      stop(error.msg, call. = FALSE)
    } else if (any(st.nm %in% real.road.names == FALSE)) {
      nm.err <- st.nm[!st.nm %in% real.road.names]
      nm.msg <- "Misspelled or invalid street name(s). See streetNames():"
      message(paste(nm.msg, paste(nm.err, collapse = ", ")))
      st.nm <- st.nm[st.nm %in% real.road.names]
    }
  }

  rd <- cholera::roads[!cholera::roads$street %in% cholera::border, ]
  cartesian.rd <- data.frame(street = rd$street, geoCartesian(rd))
  vars <- c("x", "y")
  roads.list <- split(cartesian.rd[, vars], cartesian.rd$street)

  if (is.null(street.name) | isFALSE(zoom)) {
    xlim <- NULL
    ylim <- NULL
  } else if (!is.null(street.name) & isTRUE(zoom)) {
    sel <- cartesian.rd$street %in% unique(rd[rd$name %in% st.nm, "street"])
    xlim <- range(cartesian.rd[sel, "x"])
    ylim <- range(cartesian.rd[sel, "y"])
  } else if (!is.null(street.name) & is.numeric(zoom)) {
    sel <- cartesian.rd$street %in% unique(rd[rd$name %in% st.nm, "street"])
    if (zoom == 0) {
      xlim <- range(cartesian.rd[sel, "x"])
      ylim <- range(cartesian.rd[sel, "y"])
    } else if (zoom != 0) {
      pad <- c(zoom, -zoom)
      xlim <- range(cartesian.rd[sel, "x"]) + pad
      ylim <- range(cartesian.rd[sel, "y"]) + pad

      xlim.delta <- xlim[2] - xlim[1]
      ylim.delta <- ylim[2] - ylim[1]

      if (xlim.delta <= 0 | ylim.delta <= 0) {
        xlim <- range(cartesian.rd[sel, "x"])
        ylim <- range(cartesian.rd[sel, "y"])
        message("Note: zoom = ",  zoom, " too far! Use smaller.")
      }
    }
  }

  plot(cartesian.rd[, vars], asp = 1, pch = NA, xlim = xlim, ylim = ylim)
  invisible(lapply(roads.list, lines, col = street.col))
}