[R-sig-Geo] Can you query points with a polygon?

Wed Dec 13 06:24:00 CET 2006

Yes there is more than one. I can't remember when I made the decision but I recall doing some speed tests and I picked inside.owin in the spatstat package. I think splancs and spatial might have their own versions as well. The overlay function in sp works. I think I found this too slow for what I was doing at the time. I haven't revisited this recently so it may be worth your while checking out the variations.

Tom

> -----Original Message-----
> From: r-sig-geo-bounces at stat.math.ethz.ch
> [mailto:r-sig-geo-bounces at stat.math.ethz.ch]On Behalf Of Pierce, Ken
> Sent: Wednesday, 13 December 2006 1:56 PM
> To: r-sig-geo at stat.math.ethz.ch
> Subject: [R-sig-Geo] Can you query points with a polygon?
> 
> 
> If I have a set of points from a shapefile (or generated in R) and a
> polygon from a shapefile, can I use the polygon to select the points
> that fall within it? One of the many packages must do it but I can't
> seem to figure which one.
> 
> Thanks,
> 
> Kenneth B. Pierce Jr.
> Research Ecologist
> Landscape Ecology, Modeling, Mapping and Analysis Team 
> PNW Research Station - USDA-FS 
> 3200 SW Jefferson Way,  Corvallis,  OR 97331 
> ken.pierce at oregonstate.edu
> 541 750-7393 
> http://www.fsl.orst.edu/lemma/gnnfire
> 
> 
> 
>  
> 
> -----Original Message-----
> From: r-sig-geo-bounces at stat.math.ethz.ch
> [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of
> r-sig-geo-request at stat.math.ethz.ch
> Sent: Monday, December 11, 2006 3:00 AM
> To: r-sig-geo at stat.math.ethz.ch
> Subject: R-sig-Geo Digest, Vol 40, Issue 9
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> Today's Topics:
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>    1. Re: project the lat./long. to x/y (zhijie zhang)
> 
> 
> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Mon, 11 Dec 2006 09:05:44 +0800
> From: "zhijie zhang" <epistat at gmail.com>
> Subject: Re: [R-sig-Geo] project the lat./long. to x/y
> To: Roger.Bivand at nhh.no
> Cc: r-sig-geo at stat.math.ethz.ch
> Message-ID:
> 	<2fc17e30612101705k1c06bef5of751d5764dd1d360 at mail.gmail.com>
> Content-Type: text/plain
> 
> *Dear Roger Bivand* ,
>   Your suggestions are very good, which gives me a general 
> method to do
> projections.
>   Thanks.
> 
> 
> On 12/6/06, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> >
> > On Wed, 6 Dec 2006, zhijie zhang wrote:
> >
> > > Dear friends,
> > >   I had a point pattern dataset, whose locations was defined
> > by  lat./long..
> > > In the past, I used ARCGIS to specify its coordinate 
> system and the 
> > > projection method, now i want to do it in R. I don't know 
> how to do 
> > > it, because it needs me to specify the *Geographic 
> Coordinate System
> 
> > > and the Projected Coordinate System.* Maybe i mistake the 
> > > information in ARCGIS
> > and
> > > only the projection method need to be specified because of my poor
> > knwledge
> > > on coordiante systems.
> >
> > Coordinate systems are unusually difficult to understand for
> everybody!
> >
> > In rgdal:
> >
> > EPSG <- make_EPSG()
> > EPSG[grep("Xian", EPSG$note), 1:2]
> >
> > gives a list of the known projections including "Xian",
> >
> > among which:
> >
> > CRS("+init=epsg:2384")
> >
> > looks promising. The a= and b= specify the ellipsoid used, 
> but I have 
> > not been able to find an authority to confirm that it is 
> D_Xian_1980. 
> > One way to check would be to take a long/lat value in WGS84 
> (for known
> 
> > datum) and convert it to the target projection in both 
> ArcGIS and with
> 
> > spTransform() in rgdal, and see how far they differ. I do not see 
> > anything helpful in http://www.asprs.org/resources/GRIDS - 
> referenced 
> > on the make_EPSG help page, which is often a good authority, so you 
> > may need to double-check with local sources.
> >
> > The way to go would be to make your (point?) data set into 
> a Spatial* 
> > object with a projection argument like CRS("+proj=longlat 
> > +ellps=WGS84") if the ellipsoid is correct, and use 
> spTransform to get
> 
> > to the Gauss_Kruger Xian datum representation.
> >
> > Roger
> >
> > PS. Yes, the Windows binary of the rgdal version you give below was 
> > built on R 2.4.0 (you are on Windows?). You need to 
> download a Windows
> 
> > binary package manually from 
> > http://cran.r-project.org/bin/windows/contrib/
> > (there is a 0.4-12 version for R 2.3); the same may apply to other 
> > packages.
> >
> > >
> > > ---------------------------------------------------The 
> information 
> > > in
> > ARCGIS
> > > after projecting the dataset-------
> > > Geometry Type: Point
> > >
> > > *Geographic Coordinate System:* #specify the coordinate system 
> > > GCS_Xian_1980
> > > Datum: D_Xian_1980
> > > Prime Meridian: 0
> > >
> > > *Projected Coordinate System:* Xian_1980_3_Degree_GK_CM_117E
> #specify
> > the
> > > projection method
> > > Projection: Gauss_Kruger
> > > False_Easting: 500000.00000000
> > > False_Northing: 0.00000000
> > > Central_Meridian: 117.00000000
> > > Scale_Factor: 1.00000000
> > > Latitude_Of_Origin: 0.00000000
> > > Linear Unit: Meter (1.000000)
> > >
> > 
> ----------------------------------------------------------------------
> > ------------------------------------------------------
> > > mapproject(x, y, projection="", parameters=NULL,
> > orientation=NULL)  *#only
> > > allows us to define the projected coordinate system Anybody knows 
> > > how to finish it in R? Maybe rgdal() can it, but it's a
> > liitle
> > > difficult for me*.
> > >
> > > *Example of my dataset:*
> > >
> > > ID  CLASS SOILTEM AIRTEM GHEIGHT H      *LAT     LONG*
> > > 1   1      19       20      50        30.61688 117.4140
> > > 2   1      19       21      65        30.61686 117.4140
> > > 3   2      20       22      55        30.61680 117.4139
> > > 4   3      20       26      10        30.61675 117.4139
> > > 5   4      20       23      75        30.61679 117.4140
> > > 6   1      21       21      55        30.61685 117.4141
> > >
> > > BTW, when i load the package rgdal, the following errors 
> > > appear,*where
> > is
> > > the wrong*? Does it mean i need to use the R2.4.0 version?
> > > error in load(dataFile, ns) : ReadItem 
> uncorrect$B!'(Bno class 25 
> > > Warning message:
> > > package'rgdal'is build with R2.4.0
> > > error: package'rgdal' R's input code fail
> > > error: 'rgdal'package/name space load fail$B!$(B 
> > > -------------------------------package information
> > > ----------------------------
> > > R : Version 2.3.1 (2006-06-01)
> > > rgdal_0.5-1
> > > ---------------------------------------------
> > >
> > >
> >
> > --
> > 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
> >
> >
> 
> 
> --
> With Kind Regards,
> 
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> **********
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> Zhi Jie,Zhang ,PHD
> Tel:86-21-54237149   epistat at gmail.com
> Dept. of Epidemiology,school of public health,Fudan University
> Address:No. 138 Yi Xue Yuan Road,Shanghai,China
> Postcode:200032
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