orthomap

Overview

The package orthomap contains one single function: orthomap(). It was designed to solve a common issue encountered when using the map() function of the maps package in the orthographic projection: some polygons are not correctly projected and some geographical aberrations appear in the final map (see figure below and pay attention to Russia and Antarctica). Moreover, the orthomap() function returns projected World country polygons into the SpatialPolygons format.

Installation

To install the package orthomap from GitHub, first install the package devtools from the CRAN.

### Install the < devtools > package
install.packages("devtools", dependencies = TRUE)

### Load the < devtools > package
library(devtools)

Then install the orthomap package:

### Install the < orthomap > package from GitHub
devtools::install_github("ahasverus/orthomap")

### Load the < orthomap > package
library(orthomap)

Getting started

Some useful command lines to get started:

### List the content (objects and functions) of the < orthomap > package
ls("package:orthomap")

### Open the < orthomap > package home page
help(package = "orthomap")

### Open the help file of a specific function
help(orthomap)

Usage

### World orthographic map with default settings
world <- orthomap(
  query        = NULL,
  centre       = c(0, 0),
  border.color = NA,
  border.type  = 1,
  border.size  = 0.25,
  fill         = "#909090",
  globe        = "transparent",
  grid         = TRUE,
  nx           = 10,
  ny           = 10,
  grid.color   = "#969696",
  grid.type    = 1,
  grid.size    = 0.25
)

### Short version
world <- orthomap()

### Class of the object returned
class(world)
# [1] "SpatialPolygons"
# attr(,"package")
# [1] "sp"

### Number of polygons
length(world)
# [1] 816

### Center World map based on country name
world <- orthomap(query = "South Georgia")

### Center World map based on coordinates
world <- orthomap(centre = c(20, 60))

### World map with customized graphical parameters
world <- orthomap(
  centre       = c(20, 60),
  border.color = "#bbbbbb",
  border.size  = 0.15,
  fill         = c("#0868ac", "#016c59", "#b30000", "#ae017e", "#bf812d"),
  globe        = "#b3d0d1",
  nx           = 20,
  ny           = 20,
  grid.color   = "#c2c2c2",
  mar          = rep(0, 4),
  bg           = "#999999"
)

### To customize other graphical parameters, see:
?par

Tricks and tips

How to get the correct spelling of countries?

### Get available countries names
countries <- maps::map("world", plot = FALSE)$names

length(countries)
# [1] 1627

countries[1:8]
# [1] "Aruba"                        "Afghanistan"
# [3] "Angola"                       "Angola:Cabinda"
# [5] "Anguilla"                     "Albania"
# [7] "Finland:Aland Islands:Foglo"  "Finland:Aland Islands:Eckero"

Let's take an example with France.

### Get all countries containing the string < France >
countries[grep("france", tolower(countries))]
# [1] "France:Corsica"          "France:Ile d'Oleron"
# [3] "France"                  "Greenland:Ile de France"

Here, just the first three elements correspond to the country France.

### Select items starting with the string < France >
countries[grep("^france", tolower(countries))]
# [1] "France:Corsica"      "France:Ile d'Oleron" "France"

So to center the map on metropolitan France:

### Center map on metropolitan France
world <- orthomap(query = "^france", globe = "#b3d0d1")

Note that the argument query is case insensitive.

So query = "^france" is equivalent to query = "^France" and to query = "^FRANCE".

Acknowledgments

The development of this function was inspired by the post of David on Stack Overflow. Thank you David!