[R-sig-Geo] rbind and spRbind

[Agustin Lobo]

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.

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
>>
>>
> 

-- 
Dr. Agustin Lobo
Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
LLuis Sole Sabaris s/n
08028 Barcelona
Spain
Tel. 34 934095410
Fax. 34 934110012
email: Agustin.Lobo at ija.csic.es
http://www.ija.csic.es/gt/obster