[R-sig-Geo] Error with read.GWT2nb in making KNN weights symmetrical

[Roger Bivand]

On Thu, 17 Mar 2011, Kevin Wolff wrote:

> Hi all,
>
> I have worked with R before, but admittedly not in some time.  What I am 
> trying to do is take my Geoda Nearest Neighbors Spatial weights files 
> and make them symmetrical in order to use the Spatial Lag and Spatial 
> Error functions in Geoda. Roger has been kind enough to help with this 
> in the past and I have the code to do it.  The issue I am facing 
> currently is getting R to run the code specified.  I run the first line 
> knngwt <- read.GWT2nb("1503_NN.GWT", region.id=NULL ) and get the 
> following error: "Error: could not find function "read.GWT2nb"

Well, R is case sensitive, and the function is named read.gwt2nb(), so the 
error does seem plausible. Try using the right name. Tip - try ?<name> to 
see if a function exists and is user-visible.

Roger

>
> I have installed the newest version of R (2.12) as well as installed the maptools and spdep packages which seem to run okay.
> install.packages("maptools",dependencies=TRUE)
> install.packages("spdep",dependencies=TRUE)
>
> But when I put the syntax in I get that error message.  This may be due to an error on my part in installing the required packages, but I have tried everything I have come across to no avail. I appreciate any guidance in this matter. The full code, that I am attempting to run is below.  Thank you again.   Kevin
>
> knngwt <- read.GWT2nb("1503_NN.GWT", region.id=NULL )
> class(knngwt) # "nb"
> summary(knngwt)
> print(is.symmetric.nb(knngwt))
> knngwtsym <- make.sym.nb(knngwt)
> class(knngwtsym) # "nb"
> print(is.symmetric.nb(knngwtsym))
> listw1 <- nb2listw(knngwtsym, style="B")
> class(listw1) # "listw"
> knngwtsymsn <- listw2sn(listw1)
> class(knngwtsymsn) # "spatial.neighbour"
> write.sn2gwt(knngwtsymsn, "1503_NN_SYM.GWT"
>
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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