[R-sig-Geo] Create SpatialLinesDataFrame

[Roger Bivand]

On Mon, 15 Feb 2010, Tyler Dean Rudolph wrote:

> I have searched extensively for some good examples or documentation on how
> to create a SpatialLinesDataFrame and for the life of me have found zilch.
> This does not mean there is no such thing available, it just means that
> wherever it is it is not readily accessible through the circuitous pathways
> of R help documentation or via a simple web search.

I have discussed with Achim Zeilis, who faces the same problem, the 
ethical appropriateness of mentioning our book on the Spatial Task View, 
and we've found until now that we shouldn't mention our own books. If 
opinion is that we should, and because they are in a number of university 
libraries, I can do that, and encourage Achim to do the same for 
Econometrics.

If you visit the book website (http://www.asdar-book.org), you will find 
links to code showing how to do this (chapter 2). In addition, under 
"Additional materials", you find links to course materials, especially to 
a course given at Imperial College in 2007, in which a good deal of these 
questions are covered (see "Representing Spatial Data").

Because the classes were designed as interface containers, most users do 
not need to know how to construct them from scratch, typically reading in 
data or coercing from other classes of objects. While the help pages could 
certainly be improved, we do provide a vignette that ships with the 
package, and where section 6 covers Line objects etc. See:

http://cran.r-project.org/web/packages/sp/vignettes/sp.pdf

or:

vignette("sp", package="sp")

in R.

I'm sure that Mike's answer resolves your immediate problem - this is more 
of an answer to your general question about where to look for information 
about sp classes and how to make and use them.

Hope this helps,

Roger

> As someone who
> struggles daily to achieve highly technical things with scarcely the savvy
> required, I wish there were more (or any?) examples in the documentation for
> most of the spatial packages available.  (I also wish that managing and
> manipulating Spatial objects was about 65% less complicated, but for the
> moment let's start with this)...
>
> I have a data.frame (temp) containing endpoints of animal trajectories with
> which I would like to create a SpatialLinesDataFrame for export into a GIS.
>
>> temp
>       id                 day       x        y        X2       Y2
> 1 2002007 2005-04-04 12:01:01 -300358 748992.6 -300450.8 748764.8
> 2 2002007 2005-04-04 12:01:01 -300358 748992.6 -301694.2 751728.4
> 3 2002007 2005-04-04 12:01:01 -300358 748992.6 -299983.1 749528.8
> 4 2002007 2005-04-04 12:01:01 -300358 748992.6 -300569.4 749640.7
> 5 2002007 2005-04-04 12:01:01 -300358 748992.6 -300439.0 748308.8
>
> I seem reasonably able to create a Lines object (though I can't get the ID
> argument to work for me where there are multiple records involved)....
>
>> ranlines<-apply(temp, 1,  function(x)
> Lines(Line(list(rbind(as.numeric(x[7:8]), as.numeric(x[9:10]))))))
>
>> str(ranlines[[1]])
> Formal class 'Lines' [package "sp"] with 2 slots
>  ..@ Lines:List of 1
>  .. ..$ :Formal class 'Line' [package "sp"] with 1 slots
>  .. .. .. ..@ coords: num [1:2, 1:2] -300358 -300451 748993 748765
>  .. .. .. .. ..- attr(*, "dimnames")=List of 2
>  .. .. .. .. .. ..$ : NULL
>  .. .. .. .. .. ..$ : chr [1:2] "X1" "X2"
>  ..@ ID   : chr NA
>
> Am I at least on the right track?   Unfortunately now I'm clueless as to
> what to do next because apparently Lines cannot be coerced to SpatialLines,
> and while I am normally able to figure my way out of things there is just
> nothing intuitive about this as far as I can tell.  I have tried to create
> SLDFs numerous times in the past and I have always been discouraged from
> continuing.  I can create a psp object in Spatstat but I am equally unable
> to convert that into a SLDF shape.  Terribly sorry about the rant but it's
> difficulties like these that prevent a lot of people more clueless than me
> from ever getting anywhere with R and more specifically the spatial
> stuff....
>
> Tyler
>
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>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no