R: Converter functions to build SpatialLinesDataFrame objects

ContourLines2SLDF {maptools} | R Documentation

## Converter functions to build SpatialLinesDataFrame objects

### Description

These functions show how to build converters to SpatialLinesDataFrame objects: `ArcObj2SLDF` from the list returned by the `get.arcdata` function in the RArcInfo package; `ContourLines2SLDF` from the list returned by the `contourLines` function in the graphics package (here the data frame is just the contour levels, with one Lines object made up of at least one Line object per level); and `MapGen2SL` reads a file in "Mapgen" format into a `SpatialLines` object.

### Usage

    ArcObj2SLDF(arc, proj4string=CRS(as.character(NA)), IDs)
    ContourLines2SLDF(cL, proj4string=CRS(as.character(NA)))
    MapGen2SL(file, proj4string=CRS(as.character(NA)))

### Arguments

`arc` | a list returned by the `get.arcdata` function in the RArcInfo package
`IDs` | vector of unique character identifiers; if not given, suitable defaults will be used, and the same values inserted as data slot row names
`cL` | a list returned by the `contourLines` function in the graphics package
`proj4string` | Object of class `"CRS"`; see CRS-class
`file` | filename of a file containing a Mapgen line data set

### Value

A SpatialLinesDataFrame object

### Note

Coastlines of varying resolution may be chosen online and downloaded in "Mapgen" text format from http://www.ngdc.noaa.gov/mgg/shorelines/shorelines.html, most conveniently using the interactive selection tool, but please note the 500,000 point limit on downloads, which is easy to exceed.

### Author(s)

Roger Bivand; Edzer Pebesma

### See Also

SpatialLines-class

### Examples

    #data(co37_d90_arc) # retrieved as:
    # library(RArcInfo)
    # fl <- "http://www.census.gov/geo/cob/bdy/co/co90e00/co37_d90_e00.zip"
    # download.file(fl, "co37_d90_e00.zip")
    # e00 <- zip.file.extract("co37_d90.e00", "co37_d90_e00.zip")
    # e00toavc(e00, "ncar")
    # arc <- get.arcdata(".", "ncar")
    #res <- arcobj2SLDF(arc)
    #plot(res)
    #invisible(title(""))
    res <- ContourLines2SLDF(contourLines(volcano))
    plot(res, col=terrain.colors(nrow(as(res, "data.frame"))))
    title("Volcano contours as SpatialLines")

[Package maptools version 0.9-3 Index]