[R-sig-Geo] Change Lines'IDs within a SpatialLines object

[Bastien Tran]

Thank you very much Roger, it is really helpful.

I had no idea SpatialLines (or SpatialPolygons) objects could be
manipulated this way. If I may ask, to which extent these objects can
be treated as data frames (I understand they are not?)? I may have
missed it but I haven't seen such thing in the documentation.

Incidentally I think your answer made me understand what
SpatialLinesDataFrame are (I used to think it was a different way to
store the shape's geometry but it is more about linking
attributes/variables to shapes ID's if I am correct).  It will serve
my purpose quite aptly.

Thanks a lot again, I already had more answers than I asked for.

Best regards,
Bastien

2015-12-09 17:40 GMT+01:00 Roger Bivand <Roger.Bivand at nhh.no>:
> On Wed, 9 Dec 2015, Bastien Tran wrote:
>
>> Dear all,
>>
>> I intend to make "copies" of SpatialLines object meaning I would like
>> to get the same geometry but with different IDs for the Lines.
>
>
> Please use row.names(), so here:
>
> row.names(L1) <- c("c", "d")
>
> If L1 was a SpatialLinesDataFrame, the row.names of the data slot would also
> be updated.
>
> Roger
>
>>
>> For instance using L1 from the SpatialLines example I would like to go
>> from:
>>
>>> str(L1)
>>
>> Formal class 'SpatialLines' [package "sp"] with 3 slots
>>  ..@ lines      :List of 2
>>  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
>>  .. .. .. ..@ Lines:List of 1
>>  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slot
>>  .. .. .. .. .. .. ..@ coords: num [1:3, 1:2] 1 2 3 3 2 2
>>  .. .. .. ..@ ID   : chr "a"
>>  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
>>  .. .. .. ..@ Lines:List of 1
>>  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slot
>>  .. .. .. .. .. .. ..@ coords: num [1:3, 1:2] 1 2 3 3 1.5 1
>>  .. .. .. ..@ ID   : chr "b"
>>  ..@ bbox       : num [1:2, 1:2] 1 1 3 3
>>  .. ..- attr(*, "dimnames")=List of 2
>>  .. .. ..$ : chr [1:2] "x" "y"
>>  .. .. ..$ : chr [1:2] "min" "max"
>>  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
>>  .. .. ..@ projargs: chr NA
>>
>> to
>>
>>> str(L1)
>>
>> Formal class 'SpatialLines' [package "sp"] with 3 slots
>>  ..@ lines      :List of 2
>>  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
>>  .. .. .. ..@ Lines:List of 1
>>  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slot
>>  .. .. .. .. .. .. ..@ coords: num [1:3, 1:2] 1 2 3 3 2 2
>>  .. .. .. ..@ ID   : chr "c"
>>  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
>>  .. .. .. ..@ Lines:List of 1
>>  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slot
>>  .. .. .. .. .. .. ..@ coords: num [1:3, 1:2] 1 2 3 3 1.5 1
>>  .. .. .. ..@ ID   : chr "d"
>>  ..@ bbox       : num [1:2, 1:2] 1 1 3 3
>>  .. ..- attr(*, "dimnames")=List of 2
>>  .. .. ..$ : chr [1:2] "x" "y"
>>  .. .. ..$ : chr [1:2] "min" "max"
>>  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slot
>>  .. .. ..@ projargs: chr NA
>>
>>
>> Is there a way to do so without rebuilding the SpatialLine object with
>> updated Lines objects (same Lines new IDs)? I assume it is possible to
>> update each ID slot directly in L1 somehow.
>>
>> I expected something like
>>
>> sapply(slot(L1, "lines"), function(x) assign(slot(x, "ID"),
>> paste0("copyof",slot(x, "ID")))
>>
>> to do so but I am certainly missing something about assignments in S4
>> objects.
>>
>> Thank you for any help.
>>
>> Best regards,
>>
>> Bastien Tran
>>
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>>
>
> --
> Roger Bivand
> Department of Economics, Norwegian School of Economics,
> Helleveien 30, N-5045 Bergen, Norway.
> voice: +47 55 95 93 55; fax +47 55 95 91 00
> e-mail: Roger.Bivand at nhh.no
>