In raster there are "as" methods to coerce the geometries of
SpatialPolygons and SpatialLines to a data.frame and back. I am not sure if
they are documented and whether anyone has discovered and used these; but I
found them helpful. sp would be a more natural place for such functions.

Robert

On Sun, Dec 16, 2012 at 12:47 PM, Edzer Pebesma <
edzer.pebesma@uni-muenster.de> wrote:

>
>
> On 12/16/2012 08:58 PM, Barry Rowlingson wrote:
> > On Sun, Dec 16, 2012 at 6:53 PM, Chris English <sglish@hotmail.com>
> wrote:
> >>
> >> Edzer:
> >> On Tue, Jul 17, 2012 at 2:34 PM, Agustin Lobo ~ from Barry Rowlingson
> >> wrote:
> >> To convert to SpatialLines, get the coordinates and build in the
> >> usual convoluted manner:
> >>
> >>  > s=data.frame(x=runif(10),y=1:10,z=rnorm(10))
> >>  > coordinates(s)=~x+y
> >>  > L = SpatialLines(list(Lines(list(Line(coordinates(s))),"X")))
> >>  > plot(L)
> >> Convoluted is not the same as orphaned, certainly, but one gets the
> sense that
> >> 'Line' owes its existence to matters of plotting rather than line as
> line, independent of
> >> drawing it, and this may have some import upon line analysis and the
> possibility of
> >> arriving at topology and dispensing with shared lines and the like.
> >
> >  "Line" is a non-spatial Line, made up from an ordered set of (x,y)
> > coordinate pairs. It cannot have a coordinate system assigned to it.
> >
> >  "Lines" is a list of Lines, making a non-spatial set of Line
> > segments. It too cannot have a coordinate system assigned.
> >
> >  "SpatialLines" is a spatial set of Lines, for when you have a number
> > of features each of which may be composed of several disconnected
> > segments. It can have a coordinate system assigned.
> >
> >  You are making a SpatialLines object where a single feature has a
> > single line segment. The slightly annoying
> > list(Lines(list(Line(...)))) dance is unavoidable because the lists
> > are necessary since the lists can have more than one element, but you
> > could easy create a 'SimpleSpatialLine' function that did all that. It
> > might even make sp for R 3.0.0! (SimpleSpatialPolygon might be handy
> > too...)
>
> Nice idea -- or a "simple" method that does it with whatever you feed it
> with? Or simply "c" methods, like c(Line1,Line2,Line3) creating a
> SpatialLines object?
>
> @Chris: the convolution of lines is identical to that of polygons, as is
> its lack of topology and facilities for analysis.
>
> >
> > Another possibility might be to write methods for SpatialLines that
> > takes a matrix and skips the complexity for simple cases...
>
> like, a n x 2 matrix with NA-separated lines?
>
> >
> > Barry
> >
>
> --
> Edzer Pebesma
> Institute for Geoinformatics (ifgi), University of Münster
> Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
> 8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de
> http://www.52north.org/geostatistics      e.pebesma@wwu.de
>
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