R 3.0.0 and spatial classes

Is there interest in something like this code for generating SpatialLines?
I use a variation of this fairly regularly:

SimpleSpatialLines <- function(coords.1, coords.2, proj4string =
CRS(as.character(NA))){
 coords.1 <- coordinates(coords.1)
 coords.2 <- coordinates(coords.2)
 if (nrow(coords.1) != nrow(coords.2)) stop("coords.1 must be of same
length as coords.2")
 coords.both <- cbind(coords.1, coords.2)
 coords.both <- cbind(coords.both, 1:nrow(coords.both))
 lines <- apply(X=coords.both,
                MARGIN=1,
                FUN=function(x){
                  Lines(list(Line(cbind(c(x[1], x[3]),
                                        c(x[2], x[4])))),
                        ID=x[5])})
 SpatialLines(LinesList=lines, proj4string=proj4string)
}



Regards,

Francis Markham
Australian National University
francis.markham at anu.edu.au






On 17 December 2012 06:58, Barry Rowlingson <b.rowlingson at lancaster.ac.uk>wrote:

On Sun, Dec 16, 2012 at 6:53 PM, Chris English <sglish at 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...)

Another possibility might be to write methods for SpatialLines that
takes a matrix and skips the complexity for simple cases...

Barry

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