R: Download a coastline File

download.coastline {oce}

R Documentation

Download a coastline File

Description

Constructs a query to the NaturalEarth server (see reference 1) to download coastline data (or lake data, river data, etc) in any of three resolutions.

Usage

download.coastline(
  resolution,
  item = "coastline",
  destdir = ".",
  destfile,
  server = "naturalearth",
  debug = getOption("oceDebug")
)

Arguments

`resolution`	A character value specifying the desired resolution. The permitted choices are `"10m"` (for 1:10M resolution, the most detailed), `"50m"` (for 1:50M resolution) and `"110m"` (for 1:110M resolution). If `resolution` is not supplied, `"50m"` will be used.
`item`	A character value indicating the quantity to be downloaded. This is normally one of `"coastline"`, `"land"`, `"ocean"`, `"rivers_lakes_centerlines"`, or `"lakes"`, but the NaturalEarth server has other types, and advanced users can discover their names by inspecting the URLs of links on the NaturalEarth site, and use them for `item`. If `item` is not supplied, it defaults to `"coastline"`.
`destdir`	Optional string indicating the directory in which to store downloaded files. If not supplied, `"."` is used, i.e. the data file is stored in the present working directory.
`destfile`	Optional string indicating the name of the file. If not supplied, the file name is constructed from the other parameters of the function call, so subsequent calls with the same parameters will yield the same result, thus providing the key to the caching scheme.
`server`	A character value specifying the server that is to supply the data. At the moment, the only permitted value is `"naturalearth"`, which is the default if `server` is not supplied.
`debug`	an integer specifying whether debugging information is to be printed during the processing. This is a general parameter that is used by many `oce` functions. Generally, setting `debug=0` turns off the printing, while higher values suggest that more information be printed. If one function calls another, it usually reduces the value of `debug` first, so that a user can often obtain deeper debugging by specifying higher `debug` values.

Value

A character value indicating the filename of the result; if there is a problem of any kind, the result will be the empty string.

Non-Executable Examples

library(oce)
# User must create directory ~/data/coastline first.
# As of September 2016, the downloaded file, named
# "ne_50m_coastline.zip", occupies 443K bytes.
filename <- download.coastline(destdir="~/data/coastline")
coastline <- read.coastline(filename)
plot(coastline)

Author(s)

Dan Kelley

References

The NaturalEarth server is at ⁠https://www.naturalearthdata.com⁠