Type: Package
Title: Meridional and Parallel Lines for Maps
Version: 0.4.0
Description: Create graticule lines and labels for maps. Control the creation of lines or tiles by setting their placement (at particular meridians and parallels) and extent (along parallels and meridians). Labels are created independently of lines.
License: GPL-3
Depends: sp
Imports: raster, utils, geosphere, stats, reproj (≥ 0.4.3)
Suggests: devtools, knitr, spex, testthat (≥ 2.1.0), rmarkdown, covr
VignetteBuilder: knitr
Encoding: UTF-8
BugReports: https://github.com/hypertidy/graticule/issues
URL: https://github.com/hypertidy/graticule
RoxygenNote: 7.2.3
NeedsCompilation: no
Packaged: 2023-09-25 08:29:47 UTC; mdsumner
Author: Michael D. Sumner [aut, cre]
Maintainer: Michael D. Sumner <mdsumner@gmail.com>
Repository: CRAN
Date/Publication: 2023-09-25 10:00:02 UTC

graticule: Meridional and Parallel Lines for Maps

Description

Create graticule lines and labels for maps. Control the creation of lines or tiles by setting their placement (at particular meridians and parallels) and extent (along parallels and meridians). Labels are created independently of lines.

Author(s)

Maintainer: Michael D. Sumner mdsumner@gmail.com

See Also

Useful links:

Create graticule lines.

Description

Specify the creation of lines along meridians by specifying their placement at particular lons (longitudes) and lats (latitudes) and their extents with xlim (extent of parallel line in longitude) and ylim (extent of meridional line in latitude).

Usage

graticule(lons, lats, nverts = NULL, xlim, ylim, proj = NULL, tiles = FALSE)

Arguments

lons

longitudes for meridional lines

lats

latitudes for parallel lines

nverts

number of discrete vertices for each segment

xlim

maximum range of parallel lines

ylim

maximum range of meridional lines

proj

optional proj.4 string for output object

tiles

if TRUE return polygons as output

Details

Provide a valid PROJ.4 string to return the graticule lines in this projection. If this is not specified the graticule lines are returned in their original longlat / WGS84. All segments are discretized as _rhumb_lines_ at 'getOption("graticule.mindist")' metres, which defaults to '5e4'. The arguments xlim, ylim and nverts are ignored if tiles is TRUE.

Value

SpatialLines or SpatialPolygons object

Examples

graticule()

Create graticule labels.

Description

Returns a set of points with labels, for plotting in conjuction with graticule.

Usage

graticule_labels(lons, lats, xline, yline, proj = NULL)

Arguments

lons

longitudes for meridional labels

lats

latitudes for parallel labels

xline

meridian/s for placement of parallel labels

yline

parallel/s for placement of meridian labels

proj

optional proj.4 string for output object

Details

SpatialPoints are returned in the projection of proj if given, or longlat / WGS84.

Value

SpatialPoints object with labels for downstream use

Examples

xx <- c(100, 120, 160, 180)
yy <- c(-80,-70,-60, -50,-45, -30)
prj <- "+proj=lcc +lon_0=150 +lat_0=-80 +lat_1=-85 +lat_2=-75 +ellps=WGS84"
plot(graticule(lons = xx, lats = yy,  proj = prj))
labs <- graticule_labels(lons = xx, lats = yy, xline = 100, yline = -80,  proj = prj)
op <- par(xpd = NA)
text(labs, lab = parse(text = labs$lab), pos = c(2, 1)[labs$islon + 1], adj = 1.2)
par(op)

Add longitude latitude lines to a plot

Description

Use the coordinates of the input raster to generate coordinate rasters, these are then used in a contour plot.

Usage

lonlat(
  x,
  na.rm = FALSE,
  lon = FALSE,
  lat = FALSE,
  ...,
  plot = TRUE,
  add = TRUE
)

Arguments

x

input raster

na.rm

logical, remove missing values from generated coordinates

lon

if TRUE, only longitude plotted

lat

if TRUE (and 'lon = FALSE') only latitude plotted

...

passed to [graphics::contour()]

plot

logical, plot the result

add

logical, add to current plot or instantiate one

Details

Plot is added to an existing plot by default.

Value

RasterBrick of the longitude and latitude values, two layers

(invisibly) the raster (RasterBrick) object with longitude and latitude values of the input as two layers, otherwise this function used for side-effect (drawing on a plot)

Examples

plot(c(-180, 180), c(-90, 90))
lonlat(raster::raster())

p <- raster::projectExtent(raster::raster(), "+proj=igh")
lonlat(p, add = FALSE)
lonlat(p, levels = seq(-180, 180, by  =15), add = FALSE)

lonlat(p, levels = seq(-180, 180, by = 5), add = FALSE, lon = TRUE)
lonlat(p, levels = seq(-180, 180, by = 15), add = TRUE, lat = TRUE)