[R-sig-Geo] Maptools, polylines to polygon and the .dwg format

[Nikhil Kaza]

I am not sure I understand. I havent worked with Dwg in a long time,  
but my sense is they are just geometric boundary files. There is no  
`data' attached to them.

Two options.
1. convert dwg to shapefile and do a spatial join. IF the dwg file is  
points, this what you should do.
2. if the dwg files are essentially boundaries of polygons in the  
shapefile, create a new table with ID of the polygon and count of  
diseases and then do a join with merge.



Nikhil Kaza
Asst. Professor,
City and Regional Planning
University of North Carolina

nikhil.list at gmail.com

On Jul 5, 2010, at 5:41 PM, FloydGlz wrote:

>
> Let's see if i can explain myself properly...
>
> Im doing some work on categorizing diseases per area, so i have a  
> map (a
> .dwg file) that has all the states and municipalities, and my end  
> work has
> to be the same map but with different colors depending on the number  
> of
> cases for each disease.
>
> Now, for example, in this page, http://www.gadm.org/country, you can
> download a map (i use Mexico for the example, and i download it as a  
> shape
> file), then, i load it to R with maptools and the readShapePoly  
> function;
> using this i can subset specific regions and colour it according to my
> needs, pretty easy and useful. Another great thing, is that in  
> the .dbf file
> (im not 100% is that file but im guessing it is) contains all the  
> ID's,
> which i can access with the names() function of R, and i can search  
> for a
> specific name or state, BECAUSE IT EXISTS SUCH ID.
>
> Now my problem is that i dont know how to manipulate this ID's,  
> because in
> the example they are already there, but with the data i have (the .dwg
> file), is pretty much inexistent, how do i create/edit an attribute,  
> so i
> can add it to the .shp/.dbf file? if i want to create a category named
> Municipalities, so each polygon (region of the map) has a unique  
> name, how
> do i do that?
>
> For example, in the shp file of mexico listed in the example, one  
> can create
> a map with the following code
>
> library(maptools)
> mexmap <- readShapePoly("MEX_adm2.shp")
> names(mexmap)
> df <- which(mexmap[[5]] == "Distrito Federal")
> plot(mexmap[df,])
> library(gplots)
> showpanel <- function(col){image(z=matrix(1:100, ncol=1), col=col,  
> xaxt="n",
> yaxt="n")}
> showpanel(colorpanel(6,low="skyblue",high="darkblue")) #so i can see  
> the
> colors
> colore <- colorpanel(6,low="skyblue",high="darkblue")
> colore <- rep(colore,length.out=16)
> plot(mexmap[df,],col=colore)
>
> In the end is easier because i have the names i want, and i can  
> manipulate
> the regions needed. I want to do the same with my file.
>
> I appreciate any suggestions, thank very much for your time.
>
> ------------------------------------
> Melvin Jesus Noe Gonzalez
> Undergraduate Genomics Student
> UNAM MEX
> mnoe at lcg.unam.mx
>
> -- 
> View this message in context: http://r-sig-geo.2731867.n2.nabble.com/Maptools-polylines-to-polygon-and-the-dwg-format-tp5257809p5257809.html
> Sent from the R-sig-geo mailing list archive at Nabble.com.
>
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