addGraticules: Add graticules (parallels and meridians) to a map

In FRBCesab/ecorar: Research compendium of the Loiseau, Mouquet et al.'s 2020 paper

Description

This function adds graticules (parallels and meridians) to a map and returns axes labels and coordinates.

Usage

addGraticules(
  prj = "+proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs",
  parallels = seq(-60, 60, by = 30),
  meridians = seq(-160, 160, by = 40),
  line.color = "#aaaaaa",
  line.size = 0.5,
  line.type = 1,
  add = FALSE
)

Arguments

prj	string the CRS of the map in the PROJ4 standard.
parallels	numeric vector of latitudes to add parallels.
meridians	numeric vector of longitudes to add meridians.
line.color	string color of graticules.
line.size	numeric width of graticules.
line.type	integer type of graticules.
add	boolean If TRUE, graticules are added to the map.

Value

This function returns a 2-elements list.

A first data frame for the meridians with 4 columns:

• x: the x-coordinates of meridians

• y: the y-coordinates of meridians

• label: the labels of meridians (in degrees)

• direction: the direction, i.e. W(est) or E(ast)

A second data frame for the parallels with 4 columns:

• x: the x-coordinates of parallels

• y: the y-coordinates of parallels

• label: the labels of parallels (in degrees)

• direction: the direction, i.e. S(outh) or N(orth)

Author(s)

Nicolas CASAJUS, [e-mail]

Examples

library(maps)

maps::map()
addGraticules(
  prj = "+init=epsg:4326",
  add = TRUE
)

## [[1]]
##      x      y label direction
## 1 -160 -90.00   160         W
## 2 -120 -89.95   120         W
## 3  -80 -89.90    80         W
## 4  -40 -89.85    40         W
## 5    0 -89.80     0
## 6   40 -89.75    40         E
## 7   80 -89.70    80         E
## 8  120 -89.65   120         E
## 9  160 -89.60   160         E

## [[2]]
##        x   y label direction
## 1 -180.0 -60    60         S
## 2 -179.9 -30    30         S
## 3 -179.8   0     0
## 4 -179.7  30    30         N
## 5 -179.6  60    60         N

FRBCesab/ecorar documentation built on June 2, 2021, 8:18 p.m.