[R-sig-Geo] Extract points from SpatialLines objects along with the corresponding Lines' ID

[Edzer Pebesma]

On 04/12/15 16:49, Bastien Tran wrote:
> Dear all,
> 
> I am trying to extract the points that compose a SpatialLines object along
> with the Line's ID (provided when Lines() is called).
> 
> Hoping it makes my question clearer this is what I am currently able to get
> (using the SpatialLines example):
> 
>> library(sp)
>> l1 = cbind(c(1,2,3),c(3,2,2))
>> Sl1 = Line(l1)
>> S1 = Lines(list(Sl1), ID=c("a"))
>>
>> l2 = cbind(c(1,2,3),c(3,1.5,1))
>> Sl2 = Line(l2)
>> S2 = Lines(list(Sl2), ID="b")
>>
>>
>> L1 = SpatialLines(list(S1,S2))

Try:

> as(as(L1, "SpatialPointsDataFrame"), "data.frame")
  Lines.NR Lines.ID Line.NR coords.x1 coords.x2
1        1        a       1         1       3.0
2        1        a       1         2       2.0
3        1        a       1         3       2.0
4        2        b       1         1       3.0
5        2        b       1         2       1.5
6        2        b       1         3       1.0

or alternatively:

> as(L1, "SpatialMultiPoints")@coords
$a
     [,1] [,2]
[1,]    1    3
[2,]    2    2
[3,]    3    2

$b
     [,1] [,2]
[1,]    1  3.0
[2,]    2  1.5
[3,]    3  1.0





>>
>> sapply(slot(L1, "lines"), function(x) lapply(slot(x, "Lines"),
> function(y) slot(y, "coords")))
> [[1]]
>      [,1] [,2]
> [1,]    1    3
> [2,]    2    2
> [3,]    3    2
> 
> [[2]]
>      [,1] [,2]
> [1,]    1  3.0
> [2,]    2  1.5
> [3,]    3  1.0
> 
> But I would rather like to obtain something like this:
> 
> [[1]]
>      [,1] [,2] [,3]
> [1,] "1"  "3"  "a"
> [2,] "2"  "2"  "a"
> [3,] "3"  "2"  "a"
> 
> [[2]]
>      [,1] [,2]  [,3]
> [1,] "1"  "3"   "b"
> [2,] "2"  "1.5" "b"
> [3,] "3"  "1"   "b"
> 
> If possible I would like to avoid type conversions and get a data.frame
> directly though I could indeed recreate one with these matrices, without
> information loss I assume.
> 
> Thank you in advance for any tips.
> 
> Best regards,
> Bastien
> 
> 	[[alternative HTML version deleted]]
> 
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> 

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi),  University of Münster,
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/
Spatial Statistics Society http://www.spatialstatistics.info

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