[R-sig-Geo] zerodist() fails with Projected Data

[Edzer Pebesma]

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This was a bug. svn revision 1437 on r-forge has this corrected.

Thanks for the reproducible example,

On 07/21/2013 08:29 PM, Jesse Berman wrote:
> Hi All,
> 
> I have run across an error where 'zerodist()' fails to identify
> duplicate points if data is projected under a geographic coordinate
> system (e.g. WGS84 or NAD83).  However, it works correctly if data
> has no set projection or is projected under a local or continental
> system (e.g. Albers Equal Area or Lambert Conformal Conic).  Any
> thoughts as to why this occurs (see example below)?
> 
> Jesse
> 
> /# GCS Projection, where zerodist() fails to identify duplicates.
> WGS84 also fails to work require(sp) longitude<-c(-75.518056,
> -76.952778, -77.032500, -75.558056, -75.558056) 
> latitude<-c(39.155000, 38.897222, 38.880833, 39.739444, 39.739444) 
> z<-c(12, 14, 15, 13, 19) data<-as.data.frame(cbind(longitude,
> latitude, z)) coordinates(data)=~longitude+latitude 
> proj4string(data)=CRS("+proj=longlat +ellps=GRS80 +datum=NAD83
> +no_defs +towgs84=0,0,0 +units=m") # NAD83 Geographic Coordinate
> System zerodist(data)/
> 
> /# Continental Projection on same dataset, where zerodist()
> identifies duplicates require(sp) longitude<-c(-75.518056,
> -76.952778, -77.032500, -75.558056, -75.558056) 
> latitude<-c(39.155000, 38.897222, 38.880833, 39.739444, 39.739444) 
> z<-c(12, 14, 15, 13, 19) data<-as.data.frame(cbind(longitude,
> latitude, z)) coordinates(data)=~longitude+latitude 
> proj4string(data)=CRS("+proj=aea +lat_1=20 +lat_2=60 +lat_0=40
> +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m
> +no_defs") #Continental projection system for Albers Equal Area 
> zerodist(data) /
> 
> 
> 
> ----- -------------------------------------------------------- 
> Jesse D Berman, PhD Johns Hopkins Bloomberg School of Public
> Health Department of Environmental Health Sciences Post-Doc -- View
> this message in context:
> http://r-sig-geo.2731867.n2.nabble.com/zerodist-fails-with-Projected-Data-tp7584211.html
>
> 
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> 
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> 

- -- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
83 33081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
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