Hi Jon, Thank you for your quick reply, which solved the problem with just a small change in your line of code.
Using the code below I get an error message: res$area2 = sapply(slot(res,"polygons"), function(x) slot(x, "area")) Error in `$<-`(`*tmp*`, "area2", value = c(0.000452308218606559, 0.00099334172367839 : no $<- method for object without attributes But if I use the: area2 = sapply(slot(res,"polygons"), function(x) slot(x, "area")) It works like a charm. Once again thank you for your help Regards Rui -----Original Message----- From: jon.sko...@jrc.ec.europa.eu [mailto:jon.sko...@jrc.ec.europa.eu] Sent: 13 December 2011 13:26 To: Rui Catarino Cc: r-sig-geo@r-project.org Subject: Re: [R-sig-Geo] Acessing slot information in spatialPolygon class Hi Rui, I think the following should give you what you are looking for: res$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.catar...@marlab.ac.uk > > w: http://www.scotland.gov.uk/marinescotland > <http://www.scotland.gov.uk/marinescotland> > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please visit http://www.symanteccloud.com > ______________________________________________________________________ > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo -- Jon Olav Skøien Joint Research Centre - European Commission Institute for Environment and Sustainability (IES) Global Environment Monitoring Unit Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY jon.sko...@jrc.ec.europa.eu Tel: +39 0332 789206 Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission. ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo