Draw a map of a specific country with a brochure
I would like to use the leaflet
R package to draw a map of specific countries like Italy, Spain, etc.
I checked basic examples with a function setView()
and I tried to give a vector of two values for the latitude and longitutde argument:
m <- leaflet() %>%
addTiles() %>% # Add default OpenStreetMap map tiles
setView(lng=c(46.00,48.00), lat=c(2.00,6.00), zoom = 4)
m # Print the map (map is not centered on a country, it just a test)
But I can never have a specific country on my screen like the result of this function:
library(maps)
map('italy', fill = TRUE, col = 1:10)
In the end, I just want to draw some points by geographically placing them on my maps (with latitude and longitude)
Is this possible or is the package maps
suitable for the task (although I haven't found a way to zoom in)?
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The package maps
submits the form file data as vertices. Afaik is not included in the leaflet. Therefore, you will have to get your data elsewhere. Here's my suggestion:
# Get an Italy shapefile
download.file(url = 'http://biogeo.ucdavis.edu/data/diva/adm/ITA_adm.zip',
destfile = 'italy.zip')
unzip(zipfile = 'italy.zip')
# Load libraries
library(sp)
library(rgdal)
italy <- readOGR('ITA_adm0.shp')
library(leaflet)
leaflet(italy) %>%
addPolygons() %>%
addTiles()
ADD-ON:
You can look at the vertices making up italy as saved in the package maps
with the code below.
library(maps)
italy <- map('italy', fill = TRUE, col = 1:10)
italy_coords <- cbind(italy$x, italy$y)
plot(italy_coords)
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You can just use polygons derived from maps
. Any other suitable source can of course be used, as @JanLauGe mentioned .
Once you have country-specific polygons, you can submit them to Leafet after converting them to SpatialPolygonsDataFrame
. You can also create a mask if you want to display only the area of interest.
Naturally, after that you can easily add any point or marker with standard Leaflet methods, for example addCircleMarkers( lng, lat )
.
library(ggmap)
library(leaflet)
library(magrittr)
library(maps)
library(maptools)
library(raster)
library(rgeos)
library(sp)
country <- 'italy';
zoomLevel <- 6;
# Get the map ( class is map )
ita.map <- map( country, fill = TRUE, col = 1, plot = F );
# Get the geo center for lazyness
ita.center <- geocode( "italy" );
# Extract the names from ita.map.
# e.g. "Trapani:I. Le Egadi:I. Marettimo" -> "Trapani"
# note: any other solution is fine, because we don't really need them, but they
# can be useful later
ita.map.ids <- sapply( strsplit( ita.map$names, ':' ), function(x) x[1] );
# Convert our map object to SpatialPolygons
ita.sp <- map2SpatialPolygons( ita.map, IDs=ita.map.ids,
proj4string=CRS("+proj=longlat +datum=WGS84"))
# Note: if you only need a unified polygon, it can be achieved by fortify
# ita.sp.df <- fortify( ita.sp );
# Finally convert our SpatialPolygons to SpatialPolygonsDataFrame
tmp.id.df <- data.frame( ID = names(ita.sp) );
rownames( tmp.id.df ) <- names( ita.sp );
ita.spdf <- SpatialPolygonsDataFrame( ita.sp, tmp.id.df );
# Visualize
l.ita.map <- leaflet( ita.spdf ) %>%
setView(lng = ita.center$lon, lat = ita.center$lat, zoom = zoomLevel ) %>%
addTiles() %>%
addPolygons( data = ita.spdf, weight = 1, fillColor = "blue", fillOpacity = 0.5 );
l.ita.map
####### Alternatively if a mask if needed #######
# Get a plane of the world
wld.sp <- rasterToPolygons( raster(ncol = 1, nrow = 1, crs = proj4string(ita.sp) ) );
# Cut our country polygon from the plane to get our target mask
ita.sp.mask <- gDifference( wld.sp, ita.sp );
# Convert our ita.sp.mask (SpatialPolygons) to SpatialPolygonsDataFrame
tmp.id.df <- data.frame( ID = "1" );
rownames( tmp.id.df ) <- names( ita.sp.mask );
ita.mask.spdf <- SpatialPolygonsDataFrame( ita.sp.mask, tmp.id.df );
# Coordinates of Rome
ita.rome.center <- geocode( "Rome, italy" );
# Visualize
l.ita.mask.map <- leaflet( ita.mask.spdf ) %>%
setView( lng = ita.center$lon, lat = ita.center$lat, zoom = zoomLevel ) %>%
addTiles() %>%
addPolygons( data = ita.mask.spdf, fillColor = "white", fillOpacity = 1.0, color = "black", weight = 1 ) %>%
addCircleMarkers(lng = ita.rome.center$lon, lat = ita.rome.center$lat );
l.ita.mask.map;
Thanks for @fdetsch for his suggestion
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