[R-sig-Geo] adding new values to readShapePoly() object

[Roger Bivand]

On Tue, 1 Jan 2008, Takatsugu Kobayashi wrote:

> Hi
>
> Please forgive me if I am asking a simple question.
>
> I would like to add values in a column vector to readShapePoly() object
> and show a map based on these values using spplot() or addPoly().
>
> Basically, my raw data are employment census data with the coordinates
> (X,Y).
>
> tmp1 <- read.csv("tmp1.csv",header=T)
>
> names(tmp1)
> [1] "TAZ"                "X"                  "Y"
> [4] "X_UTM"              "Y_UTM"              "Perimeter"
> [7] "Area"               "in.n"               "D_mean.dist"
> [10] "D_median.dist"      "D_mean.mean.time"   "D_mean.median.time"
> [13] "out.n"              "O_mean.dist"        "O_median.dist"
> [16] "O_mean.mean.time"   "O_mean.median.time"
>
>
> map <- readShapePoly("Akron",proj4string=CRS("+proj=longlat
> +datum=NAD27"))
> names(map)
>
>
> [1] "SOURCELYR" "SHAPECODE" "COUNTY"    "SHORTLAB"  "LONGLAB"
> "X"
> [7] "Y"         "X_UTM"     "Y_UTM"     "Perimeter" "Area"
>
> tmp1/tmp2 and map have the same nrows and the same coordinates (X,Y).
>
> Any suggestions? Should I modify .dbf files before loading .shp files?

Look at ?"spCbind-methods", these methods are in the maptools package. The 
key thing is to make sure that the row names of tmp1 and tmp1 match those 
of slot(map, "data"), which is also a data frame. They will be re-ordered 
if need be, but must agree. You will see that match() is used in the 
example on the help page. In the example, the IDvar= argument is used in 
readShapePoly(), but you can also use spChFIDs-methods for changing the 
IDs.

Roger


> Or are there functions like join_table in ArcGIS? Or should I convert
> tmp1 into a polypoint object and overlay it on map?
>
> Thank you very much.
>
> Takatsugu
>
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-- 
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