[R-sig-Geo] Acessing slot information in spatialPolygon class

[jon.skoien at jrc.ec.europa.eu]

Hi Rui,

I think the following should give you what you are looking for:
res$area2 = sapply(slot(res,"polygons"), function(x) slot(x, "area"))

Cheers,
Jon

On 13-Dec-11 13:50, Rui Catarino wrote:
> Dear all,
>
>
>
> This may seem a very obvious question but I'm suck and for the past 2h I
> haven't been able of solving the problem. So for the sake of
> productivity I'll ask for some help:
>
>
>
> I have a SpatialPolygon Class that looks like(see bellow) in the example
> below I have only 2 polygons but they will be thousands. What I'm trying
> to achieve is a list with the total area of each polygon.
>
>
>
> Thanks in advance
>
>
>
>> str(res)
> Formal class 'SpatialPolygons' [package "sp"] with 4 slots
>
>    ..@ polygons   :List of 2
>
>    .. ..$ :Formal class 'Polygons' [package "sp"] with 5 slots
>
>    .. .. .. ..@ Polygons :List of 9
>
>    .. .. .. .. ..$ :Formal class 'Polygon' [package "sp"] with 5 slots
>
>    .. .. .. .. .. .. ..@ labpt  : num [1:2] 3.19 51.68
>
>    .. .. .. .. .. .. ..@ area   : num 8.96e-05
>
>    .. .. .. .. .. .. ..@ hole   : logi FALSE
>
>    .. .. .. .. .. .. ..@ ringDir: int 1
>
>    .. .. .. .. .. .. ..@ coords : num [1:5, 1:2] 3.18 3.18 3.19 3.2 3.18
> ...
>
> .
>
> .
>
> .
>
>
>
>    .. .. .. ..@ plotOrder: int [1:9] 9 8 2 3 1 4 7 5 6
>
>    .. .. .. ..@ labpt    : num [1:2] 3.14 51.67
>
>    .. .. .. ..@ ID       : chr "2"
>
>    .. .. .. ..@ area     : num 0.000993
>
>    ..@ plotOrder  : int [1:2] 2 1
>
>    ..@ bbox       : num [1:2, 1:2] 3.09 51.66 3.26 51.73
>
>    .. ..- attr(*, "dimnames")=List of 2
>
>    .. .. ..$ : chr [1:2] "x" "y"
>
>    .. .. ..$ : chr [1:2] "min" "max"
>
>    ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
>
>    .. .. ..@ projargs: chr NA
>
>
>
>
>
>
>
>
>
>
>
> Rui Catarino
>
> Scientific Officer
>
> Fishery Systems Group
>
> Marine Scotland - Science
>
>
>
> Scottish Government | 36 |B |Marine Laboratory, PO Box 101| 375,
> Victoria Road | Aberdeen AB11 9DB
>
>
>
> Tel:  +44 (0)1224 295572
>
> Mob:+44 (0)7530 240666
>
> Fax: +44 (0)1224 295511
>
> e: r.catarino at marlab.ac.uk
>
> w: http://www.scotland.gov.uk/marinescotland
> <http://www.scotland.gov.uk/marinescotland>
>
>
>
>
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-- 
Jon Olav Skøien
Joint Research Centre - European Commission
Institute for Environment and Sustainability (IES)
Global Environment Monitoring Unit

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