[R-sig-Geo] combining polygons from shapefiles...

[Sean O'Riordain]

Hello again,

I've tried
    new.refs.for.CA <-
as.character(seq(from=max(as.numeric(row.names(LA)))+1,length=nrow(CA)))
# which takes about 0.15 secs...
    ca1 <- spChFIDs(CA, new.refs.for.CA)
# has been running now for more than 48 minutes (or at least 48 mins
CPU on this winbox)  is this right?
# It was running for about 15minutes and then I tried restarting it in
a cleaner
# environment... but it's still taking *ages*
#
# it was my intention then of saying
    S1 <- spRbind(LA, ca1)

but both LA and CA have about 12,000 rows... and it's been running now
for quite a few minutes and I'm surprised it hasn't finished... is
this "normal" ?

Thanks,
Sean


On Wed, Dec 2, 2009 at 3:18 PM, Sean O'Riordain <seanpor at acm.org> wrote:
> Thanks Roger,
>
>> head(row.names(LA))
> [1] "0" "1" "2" "3" "4" "5"
>> head(row.names(CA))
> [1] "0" "1" "2" "3" "4" "5"
>>
>
> I'll have a look at these and get back with my results.
>
> Kind regards,
> Sean
>
>
> On Wed, Dec 2, 2009 at 3:07 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>> On Wed, 2 Dec 2009, Sean O'Riordain wrote:
>>
>>> Good afternoon,
>>>
>>> I've been making good progress in the last few weeks thanks to this
>>> list, along with Roger and Adrians' books and some great geo-packages.
>>>
>>> I'm trying to combine some shapefiles...
>>>
>>> library(maptools)
>>> CA <- readShapePoly('ca.shp')
>>> LA <- readShapePoly('la.shp')
>>>
>>> Now I want to combine these two into a bigger object...
>>>
>>> I've searched the books and the internet and I've tried a number of
>>> things... including...
>>>
>>>> class(LA)
>>>
>>> [1] "SpatialPolygonsDataFrame"
>>> attr(,"package")
>>> [1] "sp"
>>>>
>>>> class(CA)
>>>
>>> [1] "SpatialPolygonsDataFrame"
>>> attr(,"package")
>>> [1] "sp"
>>>>
>>>>    S1 <- unionSpatialPolygons(CA, LA)
>>>
>>> Loading required package: gpclib
>>> General Polygon Clipper Library for R (version 1.4-4)
>>>       Type 'class ? gpc.poly' for help
>>>
>>> Error in unionSpatialPolygons(CA, LA) : input lengths differ
>>>>
>>>>
>>>> S1 <- spRbind(CA, LA)
>>>
>>> Error in spRbind(as(obj, "SpatialPolygons"), as(x, "SpatialPolygons")) :
>>>  non-unique polygon IDs
>>>>
>>
>> Correct. Look at row.names(CA) and row.names(LA). Do something of your
>> choice to disambiguate them and re-assign with spChFIDs() - since you refer
>> to the ASDAR book, there is an example in chapter 5, sections 5.4 & 5.5, pp.
>> 120-126. You'll also see that your reading of how to use
>> unionSpatialPolygons() did not agree with that in the function, which is to
>> dissolve Polygons objects within an existing SpatialPolygons object.
>>
>> Hope this helps,
>>
>> Roger
>>
>>>
>>> Any ideas please?
>>>
>>> Thanks in advance!
>>> Sean
>>>
>>> _______________________________________________
>>> R-sig-Geo mailing list
>>> R-sig-Geo at stat.math.ethz.ch
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>
>>
>> --
>> 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
>>
>>
>