R/plotPointWithInset.R

In bcgov/bcgroundwater: Analyse B.C. Groundwater Level Data

# Copyright 2015 Province of British Columbia
# 
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
# http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and limitations under the License.

#' Plot a point on a map with an overview inset
#'
#' Plot a point on a map with an inset in the top right corner showing an 
#' overview of a larger area.
#' 
#' @param  long Longitude (dd) of point
#' @param  lat Latitude (dd) of point
#' @param  pointColour The colour of the point
#' @param  bigMap ggmap of the zoomed in area that will comprise the large map
#' @param  overviewMap ggMap of large area that will be in the inset.  If not
#'   provided, will be generated using overviewExtent
#' @param  overviewExtent The extent (left, botton, right, top) of the large
#'   area that will be in the inset. Default is British Columbia
#' @param  opts Additional options to pass to ggplot2
#' @export
#' @return A ggmap object.

plot_point_with_inset <- function(long, lat, pointColour, bigMap=NULL, overviewMap=NULL, overviewExtent=c(-139,48,-114,60), opts=NULL) {

  mapExtent <- c(long-2, lat-1, long+2, lat+1)
  insExtentR <- abs(mapExtent[3]-mapExtent[1])*.95+mapExtent[1]
  insExtentL <- abs(mapExtent[3]-mapExtent[1])*.6+mapExtent[1]
  insExtentT <- abs(mapExtent[4]-mapExtent[2])*.95+mapExtent[2]
  insExtentB <- abs(mapExtent[4]-mapExtent[2])*.7+mapExtent[2]
  
  ## Use retry functions, as get_map sometimes fails. From here:
  ## http://stackoverflow.com/a/3151766/1736291
  
  retry <- function(.FUN, max.attempts = 3, sleep.seconds = 0.5) {
    expr <- substitute(.FUN)
    retry_expr(expr, max.attempts, sleep.seconds)
  }
  
  retry_expr <- function(expr, max.attempts = 3, sleep.seconds = 0.5) {
    x <- try(eval(expr))
    if(inherits(x, "try-error") && max.attempts > 0) {
      Sys.sleep(sleep.seconds)
      return(retry_expr(expr, max.attempts - 1))
    }
    x
  }
  
  if (is.null(overviewMap)) {
    overviewMap <- retry(get_map(location=overviewExtent
                                 , scale=1, maptype='terrain'
                                 , source = 'google'),5,5)
  }
  
  if (is.null(bigMap)) {
    bigMap <- retry(get_map(location=mapExtent, scale=1 
                            , maptype='terrain'
                            , source = 'google'),5,5)
  }

  
  inset <- ggmap(overviewMap, extent='device') + 
    coord_map(xlim=overviewExtent[c(1,3)], ylim=overviewExtent[c(2,4)]) + 
    annotate("rect", xmin = mapExtent[1], xmax = mapExtent[3]
             , ymin = mapExtent[2], ymax = mapExtent[4]
             , alpha=0.3, colour="black", size=0.2) +
#     geom_point(x=long, y=lat, colour=pointColour, size=2) + 
    theme(panel.border=element_rect(fill=NA, colour = "black", size=0.5))
  
  mapPlot <- ggmap(bigMap, extent='panel') + 
    geom_point(x=long, y=lat, fill=pointColour, colour="#3182BD", shape=21, size=2.5) + 
    theme(panel.border=element_rect(fill=NA, colour = "black", size=0.5)) + 
    labs(x=NULL, y=NULL) + opts +
    inset(ggplotGrob(inset), xmin = insExtentL, xmax = insExtentR
          , ymin = insExtentB, ymax = insExtentT)
  
  return(mapPlot)
}