Package 'graticule'

graticule: graticule lines for maps

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)

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