[GRASS-stats] Identifing lines with cats in SpatialLinesDataFrame

[Jarosław Jasiewicz]

Hi!

problem concern   lines imported to from GRASS, we assume that every 
line has its own category

As I rot in the one of the sp man, lines ARE NOT coneted with its 
atributes so this means that are not identified by its category, but I 
tried on small sample where I calculate generalised direction of line:

dirs=c()
for (i in 1:length(v at lines)) {
    tv=coordinates(v)[[i]][[1]]
    tl=lm(tv[,1]~tv[,2]) #dir as coef
    td=atan(coef(tl)[2])*(180/pi) #coef to degrees
    dirs=c(dirs,td) vector with degrees
... 
}

lins=data.frame(v$cat,dirs)

I checked direcitons and its look that categories are well subsripted to 
its lines

Is that assumption correct? - I of course every line have its own category??
And what about identifing lines with its ID it is its ID from GRASS??? 
suppose not.

Jarek

P.S here is piece  of SpatialLinesDataFrame:

Formal class 'SpatialLinesDataFrame' [package "sp"] with 4 slots
  ..@ data       :'data.frame': 30 obs. of  3 variables:
  .. ..$ cat    : num [1:30] 10 107 115 140 158 191 206 207 210 227 ...
  .. ..$ rzad   : num [1:30] 1 1 3 1 3 1 2 1 1 1 ...
  .. ..$ link_to: num [1:30] 11 107 11 140 115 191 158 207 210 227 ...
  ..@ lines      :List of 30
  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
  .. .. .. ..@ Lines:List of 1
  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slots
  .. .. .. .. .. .. ..@ coords: num [1:5, 1:2] 3592150 3592130 3592110 
3592090 3591850 ...
  .. .. .. ..@ ID   : chr "0"
  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
  .. .. .. ..@ Lines:List of 1
  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slots
  .. .. .. .. .. .. ..@ coords: num [1:6, 1:2] 3590210 3590210 3590190 
3590190 3590170 ...
  .. .. .. ..@ ID   : chr "1"
  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
  .. .. .. ..@ Lines:List of 1
  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slots
  .. .. .. .. .. .. ..@ coords: num [1:8, 1:2] 3592110 3591930 3591930 
3591910 3591910 ...
  .. .. .. ..@ ID   : chr "2"
  .. ..$ :Formal class 'Lines' [package "sp"] with 2 slots
  .. .. .. ..@ Lines:List of 1
  .. .. .. .. ..$ :Formal class 'Line' [package "sp"] with 1 slots
  .. .. .. .. .. .. ..@ coords: num [1:5, 1:2] 3590430 3590350 3590210 
3590190