sl.load.naturalearth: Load Natural Earth Data

In helgegoessling/spheRlab: Spherical Geometry, Analysis, and Plotting of Geoscientific Data on Arbitrary Grids

Load Natural Earth Data

Description

Load (read) and/or download Natural Earth data.

Usage

sl.load.naturalearth(what="all", resolution="medium", poly.split=TRUE, naturalearth.dir="~/naturalearthdata", force.download=FALSE, download.if.missing=TRUE, download.baseurl="https://www.naturalearthdata.com/http//www.naturalearthdata.com/download", read=TRUE, verbose=TRUE)

Arguments

what	a character or character vector specifying which type of Natural Earth data to load, e.g., 'coastline'. To list all possible values for the specified resolution, set what='list'. If what='all', all types available for the specified resolution are loaded.
resolution	a character or character vector sepcifying which resolution(s) to use. Possible values are 'coarse' (1:110Mio), 'medium' (1:50Mio; default), and 'fine' (1:10Mio).
poly.split	a logical value indicating whether polygon objects (e.g. if what='land') are to be split into small polygons before reading. Default is TRUE. If the splitting for a specific dataset is done for the first time, sl.polygon.split() is called (and optionally sl.polygon.mergehole() for polygons that include holes), and an R-object with the splitted polygons is saved in naturalearth.dir. This can take some time, highly depending on the polygon resolution. If such an object already exists (and force.raw2split=FALSE), the object is loaded instead of splitting the raw polygons again.
naturalearth.dir	a character specifying the local Natural Earth data directory. If data are downloaded from the internet, they will be save to this directory; if it does not yet exist, it will be created. Default is NULL, in which case such a value is sourced from ./spheRlab if it exists, and if not it's assumed that naturalearth.dir='~/naturalearthdata'.
force.raw2split	a logical value specifying whether to redo the polygon splitting even if a corresponding splitted-polygons R-object already exists. Default is FALSE. Only relevant if a polygon object is specified (e.g. if what='land') and poly.split=TRUE.
force.shape2raw	a logical value specifying whether to redo the conversion from the original Natural Earth shape file to an (raw, that is, not splitted) R-object if the latter already exists. Default is FALSE.
force.download	a logical value indicating whether or not to download the data from the internet, even if it already exists locally, to replace the local file. This can be useful when updates are available. By default, force.download=FALSE .
download.if.missing	a logical value indicating whether or not to download the data from the internet if it is missing locally. By default, download.if.missing=TRUE .
download.baseurl	a character specifiying the internet base URL from which to download the data.
read	a logical value indicating whether or not to load (read) tha data. If FALSE, data are only downloaded (if the corresponding arguments are set accordingly).
verbose	a logical value indicating whether or not to print more information.

Details

This function, together with sl.plot.naturalearth, enables using the openly available and free-to-use Natural Earth data (https://www.naturalearthdata.com) - including coastlines, rivers, land and ocean polygons, and much more - in spheRlab. This function is also invoked from sl.plot.naturalearth if needed, so it does not need to be used explicitly to plot Natural Earth data.

If read=TRUE, the package rgdal is needed to read the shape file(s).

Value

If read=TRUE, a named list with each element corresponding to one Natural Earth data set, with naming convention 'resolution_what'. List elements are return values of the rgdal function readOGR().

Author(s)

Helge Goessling

References

https://www.naturalearthdata.com

See Also

sl.plot.naturalearth

Examples

# load coastlines at coarse resolution:
load.res = sl.load.naturalearth(what="coastline",resolution="coarse")

# list all possible 'what' values for fine resolution:
sl.load.naturalearth(what="list",resolution="fine")

helgegoessling/spheRlab documentation built on April 8, 2024, 8:34 a.m.