R/plot_functions.R

In jwbannister/owensMaps:

#' Get coordinate ranges for square plot around polygon.
#' 
#' @param polys. Data frame. Points defining polygons of interest.
#' @param external_points Data frame. *x* and *y* coordinates of points external 
#' to polygons to be included in plot range. 
#' @return A list with the x and y ranges for a sqaure plot around the areas of 
#' interest.
get_plot_range <- function(polys, external_points=NULL){
  p.temp <- ggplot(polys, aes(x=x, y=y)) + geom_path() +
    geom_point(data=external_points)
  info <- ggplot_build(p.temp)
  plot_xrange <- info[[2]]$ranges[[1]]$x.range
  plot_yrange <- info[[2]]$ranges[[1]]$y.range
  maxspan <- max(c(plot_xrange[2] - plot_xrange[1], 
                   plot_yrange[2] - plot_yrange[1]))
  midpoint <- c(mean(plot_xrange), mean(plot_yrange))
  xrange <- c(midpoint[1] - (maxspan/2), 
              midpoint[1] + (maxspan/2))
  yrange <- c(midpoint[2] - (maxspan/2), 
              midpoint[2] + (maxspan/2))
  plot.range <- list(x=xrange, y=yrange)
  plot.range
}