Suggest (strongly) that you move this question to r-sig-geo. Much more appropriate there, and more people there are more familiar with this kind of work. But ... I suspect you want gIntersection(), not gIntersects().
-Don -- Don MacQueen Lawrence Livermore National Laboratory 7000 East Ave., L-627 Livermore, CA 94550 925-423-1062 On 3/27/15, 7:16 AM, "Walter Anderson" <wandrso...@gmail.com> wrote: >-----BEGIN PGP SIGNED MESSAGE----- >Hash: SHA1 > >Hello all, > >I am attempting to automate an analysis that I developed with ArcInfo >using R and the gdal and geos packages (or any other) if possible. > >Here is the basic process > >I have a shape file (lines) that defines the limits of all of the >projects with each project having a unique identifier. > >I have another shape file (polys) that contains total population and >low income population and represent Census block groups. This shape >file has an area field which has the acreage of the total block group. > >Process > >Step 1. >I then buffer these project lines to create a second shape file that >represents the 'footprint' of the project. (Creates polys). > >Step 2. >In ArcInfo, I perform an intersection of the two shape files >(footprint and census blocks) and this creates a third shape file >which has a unique polygon for every project/census block intersection. > >Step 3. >I then perform an area calculation (acres) on this new poly shape file >and use this calculated area divided by the original area of the >associated census block group to apportion the two population datum to >this new polygon. > >Step 4. >Finally, I sum the two population datums for each of the projects from >the attribute table of this final shape file. > >When I try to replicate the above procedure I run into a problem with >Step 2 when I use what I think is the appropriate command: > >gIntersects(buffered_projects, census_blocks, byID=TRUE) > >This command is producing a matrix of each project/census block >combination and only providing me a true/false indication. Is there >any way to replicate the process from ArcInfo that I outlined above >within R? > >Walter Anderson >-----BEGIN PGP SIGNATURE----- >Version: GnuPG v1 > >iQIcBAEBAgAGBQJVFWYWAAoJEHfnxjvhypCiMc8P/2Dsja+h4RKuR7ygHx+oI+4/ >oEIxl/NtnHwPh6szyL6CBndSYI6hvdWWwBUm86IsJLmLSSFivB1Ru54nkFq+kfKL >tWpxyOAXNZoa2xn1ADaG1ChFiY/hF937zlTTv8D3a5pYAnYtTeyg6UJ3AuHsfjqG >PbFAg6T+QD3AlJvV73JGmEchgYoj7NlxiEmdcfB3X9cgLMMOCsfLgm4d5g5J/mhh >LKZm3Xg9+eXEjPJazHYB9xc0+AF8Jp6SH9XnnZ/DMFN3DuyR3KuTJr6YnHUKvtUs >o/Uog3zAGuVUDqNwF1H9+WNuz4Fm7XXiHl4xX0n9faE3niTe2b63bVn/Ueiyofb9 >ky3wIpAr412/Ne3dtMtSDPkE3w2TsdIUKki2VP9duXB/4vEtHHXvQxNtfKdKmlYX >cnyyK/1ZwULiwWhyxZKJNUd6N2GyLYJ8MmJ7AXnT7EboJjNkhNta1BhWBE9Kzx8p >fUN1UwS8P96iFXztgg2jw3aYTPdPIp9rFYFJax5nKCl6n+YbjUw11GuO6F4lqNDv >PoLllcKkmsGWFo04P0TbS+x1zhc0wmyMn2EV8FcIXJ/80pqT/dWwksbjTfrQGoWx >Xo1m1vTR2LVVrdf0vSkWnxHA3xVQPv7YH5erVNBGWvuhgbLRx8j7MPUp7lFHOJvQ >bq1VJbpnZFRvJyZfII2p >=cZWI >-----END PGP SIGNATURE----- > >______________________________________________ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
