[R-sig-Geo] rbind and spRbind
Roger Bivand
Roger.Bivand at nhh.no
Sun Jul 27 21:31:38 CEST 2008
On Sun, 27 Jul 2008, Agustin Lobo wrote:
> Acceptable, yes, but perhaps we should choose
> one or the other and, for sure, document the difference
> between spRbind and rbind.
> Personally, I find a bit odd spRbind() in that you get 2
> variables that you were not seeing in data slot (I understand
> they are there as coordinates) of the original
> objects. This is not " rbind-like". But perhaps
> there are advantages that I'm not considering.
> Just wanted to point this out and make sure
> there were not other consequences at choosing
> between both functions.
rbind tries to be "like" rbind. Note that there is no default rbind
generic method in base R - it is just a function. The original function is
mean to join vectors and matrices by stacking them by row. It has no
concept of anything other than the data. There are issues with stacking
ordered objects by row, be they time series or whatever - so it isn't
clear how this ought to be done. The rbind and spRbind methods for
Spatial* objects try to help, but because user needs differ, no choices
will meet all needs. As I said, the addition of the coordinates comes from
the behaviour of the coercion method for SpatialPointsDataFrame to
data.frame.
There are no single good solutions here, perhaps other than dropping any
similarity to the base rbind, IMHO.
Roger
>
> Also, sorry for not having included this info:
>
>> str(ika1v4geo)
> Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
> ..@ data :'data.frame': 693 obs. of 23 variables:
> .. ..$ IKAPUNTO: int [1:693] 1 2 3 4 5 6 7 8 9 10 ...
> .. ..$ IKAID : num [1:693] 1 1 1 1 1 1 1 1 1 1 ...
> .. ..$ CN : chr [1:693] "Ivasichi" "Ivasichi" "Ivasichi"
> "Ivasichi" ...
> .. ..$ dia : chr [1:693] "2008-01-30" "2008-01-30" "2008-01-30"
> "2008-01-30" ...
> .. ..$ hora_obs: chr [1:693] " 8:48:21" " 8:55:17" " 9:00:22" " 9:07:13"
> ...
> .. ..$ GPSID : chr [1:693] "1-20080328-115" "1-20080328-116"
> "1-20080328-117" "1-20080328-118" ...
> .. ..$ GPS : int [1:693] 1 1 1 1 1 1 1 1 1 1 ...
> .. ..$ N_PUNTO : int [1:693] 115 116 117 118 119 120 122 123 124 125 ...
> .. ..$ GUIA : chr [1:693] "Endracio" "Endracio" "Endracio"
> "Endracio" ...
> .. ..$ MONITOR : chr [1:693] "Julio Vie" "Julio Vie" "Julio Vie" "Julio
> Vie" ...
> .. ..$ COD_SP_C: int [1:693] 29 9 10 29 8 8 28 8 28 29 ...
> .. ..$ SP_C : chr [1:693] "tatu" "jochi colorado" "jochi pintado"
> "tatu" ...
> .. ..$ COD_OBS : int [1:693] 5 5 5 5 6 6 6 7 6 8 ...
> .. ..$ OBS : chr [1:693] "huella" "huella" "huella" "huella" ...
> .. ..$ N : num [1:693] 1 1 1 1 1 1 1 1 1 1 ...
> .. ..$ VULN : int [1:693] 1 1 NA 1 3 3 NA 3 NA 1 ...
> .. ..$ VULNT : num [1:693] 1 1 NA 1 3 3 NA 3 NA 1 ...
> .. ..$ CL : num [1:693] 1 1 1 1 1 1 1 1 1 1 ...
> .. ..$ A : num [1:693] 8 8 8 8 8 8 8 8 8 8 ...
> .. ..$ H : num [1:693] 1.91 1.91 1.91 1.91 1.91 ...
> .. ..$ D : num [1:693] 0.719 0.719 0.719 0.719 0.719 ...
> .. ..$ S : num [1:693] 4 4 4 4 4 4 4 4 4 4 ...
> .. ..$ V : num [1:693] 34 34 34 34 34 34 34 34 34 34 ...
> ..@ coords.nrs : int [1:2] 8 9
> ..@ coords : num [1:693, 1:2] 724547 724413 724367 724282 724225 ...
> .. ..- attr(*, "dimnames")=List of 2
> .. .. ..$ : NULL
> .. .. ..$ : chr [1:2] "UTMX" "UTMY"
> ..@ bbox : num [1:2, 1:2] 716934 8303862 735638 8325272
> .. ..- attr(*, "dimnames")=List of 2
> .. .. ..$ : chr [1:2] "UTMX" "UTMY"
> .. .. ..$ : chr [1:2] "min" "max"
> ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
> .. .. ..@ projargs: chr NA
>
> Thanks!
>
> Agus
>
> Roger Bivand wrote:
>> On Sat, 26 Jul 2008, Danlin Yu wrote:
>>
>> > Agustin:
>> >
>> > Since you are using the sp method for binding, I suppose the coordinates
>> > (in UTM project according to the name) are added automatically (as the
>> > added two new names are UTMX and UTMY). Why not check these two values
>> > to see what's in them.
>>
>> Yes, that's right. Your (cryptic) SPDF is a SpatialPointsDataFrame (could
>> be Pixels or Polygons too ...), where the as(, "data.frame") coercion
>> method adds back the columns "hidden" by the coordinates()<- assignment
>> step earlier. spRbind uses the coercion method, rbind grabs the data slot
>> with the @ operator. Both are acceptable.
>>
>> Roger
>>
>> >
>> > Hope this helps.
>> >
>> > Danlin
>> >
>> >
>> > Agustin Lobo wrote:
>> > > I'm a bit confused with the following:
>> > >
>> > > I have a SPDF object ika1v4
>> > >
>> > > > dim(ika1v4geo at data)
>> > > [1] 693 23
>> > > > dim(ika1v4geo)
>> > > [1] 693 23
>> > >
>> > > Then I do an rbind:
>> > >
>> > > > a <- rbind(ika1v4geo,ika1v4geo)
>> > > > dim(a)
>> > > [1] 1386 23
>> > > > dim(a at data)
>> > > [1] 1386 23
>> > >
>> > > But spRbind introduces 2 variables:
>> > > > a2 <- spRbind(ika1v4geo,ika1v4geo)
>> > > > dim(a2)
>> > > [1] 1386 25
>> > > > dim(a2 at data)
>> > > [1] 1386 25
>> > >
>> > > > names(a at data)
>> > > [1] "IKAPUNTO" "IKAID" "CN" "dia" "hora_obs" "GPSID"
>> > > [7] "GPS" "N_PUNTO" "GUIA" "MONITOR" "COD_SP_C" "SP_C"
>> > > [13] "COD_OBS" "OBS" "N" "VULN" "VULNT" "CL"
>> > > [19] "A" "H" "D" "S" "V"
>> > > > names(a2 at data)
>> > > [1] "IKAPUNTO" "IKAID" "CN" "dia" "hora_obs" "GPSID"
>> > > [7] "GPS" "UTMX" "UTMY" "N_PUNTO" "GUIA" "MONITOR"
>> > > [13] "COD_SP_C" "SP_C" "COD_OBS" "OBS" "N" "VULN"
>> > > [19] "VULNT" "CL" "A" "H" "D" "S"
>> > > [25] "V"
>> > > >
>> > > Why? Which are the differences between rbind and spRbind?
>> > >
>> > > Thanks!
>> > >
>> > > Agus
>> >
>> >
>>
>
>
--
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
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