Generate map of UK NRFA stations

GenerateMap.R

#' Generate map of gauging stations.
#'
#' @author Claudia Vitolo <[email protected]>
#'
#' @description This function takes as input a table of UK NRFA stations (output of getStationSummary() function) and generates a map using leaflet javascript library. 
#'
#' @param selectedStationSummary This is the data.frame containing at least a column called "gridReference" (in which OS Grid references are stored) with 1 row for each station. Alternatively the table could contain 2 columns called "Latitude" and "Longitude" containing the coordinates of stations in WGS84, with 1 row for each station.
#'
#' @return displays a map 
#' 
#' @examples
#' myStations <- GetStationSummary(lonMin=-1, lonMax=1, latMin=51, latMax=49)
#' GenerateMap(myStations)
#' 

GenerateMap <- function(selectedStationSummary){
  
  library(devtools)
  if(!require(rCharts)) install_github('ramnathv/rCharts')
  
  # Load packages and sample data
  library(zoo)
  library(rCharts)
  
  coords <- NULL
  
  if ("Latitude" %in% names(selectedStationSummary) & "Longitude" %in% names(selectedStationSummary)) {
    
    coords <- data.frame("Latitude"=unlist(selectedStationSummary$Latitude), "Longitude"=unlist(selectedStationSummary$Longitude))
    
  }else{
    
    if ("gridReference" %in% names(selectedStationSummary)) {
      
      gridref <- unlist(selectedStationSummary$gridReference)
      
      coords <- data.frame("Latitude"=unlist(lapply(gridref,function(x) OSG2LatLon(OSGParse(unlist(x)))[1])), "Longitude"=unlist(lapply(gridref,function(x) OSG2LatLon(OSGParse(unlist(x)))[2])))
      
    }else{
      
      message("Provide a table with at least 1 column called gridReference.")
      
    }
    
  }
  
  if (!is.null(coords)){
    
    centerCoords <- c(mean(coords$Latitude),mean(coords$Longitude))
    
    myMap <- rCharts::Leaflet$new()
    myMap$tileLayer(provider = 'Stamen.TonerLite')    
    myMap$setView(centerCoords, zoom = 6)
    
    for (nStations in 1:dim(selectedStationSummary)[1]) {
    
      myMap$marker(c(coords$Latitude[[nStations]],coords$Longitude[[nStations]]), 
                   bindPopup = paste("<p> ", selectedStationSummary$name[[nStations]],
                                     " id: ", selectedStationSummary$id[[nStations]],
                                     " </p>", sep="") )
      
    }     
    
    myMap
    
  }
  
}