inverse distance weights matrix

Thank you Roger,

I've posted the original shape file for the dataset on the website at:
http://web.ics.purdue.edu/~twgriffi/R_matrix.htm

One shape file is projected while the other is not; however both sets of
*.dbf are identical and contain both decimal degrees and Northing and
Easting in meters.  

I chose a <=75 meter distance threshold and a power=1.  

The final inverse distance matrix was row standardized so it is not
symmetric. The weight characteristics you list below are nearly
identical to those that SpaceStat provides.  

d75

inMAT <- matrix(scan("cottonID75wm", sep=","), nrow=2451, ncol=2451, 

range(rowSums(inMAT))

d75MAT <- nb2mat(d75, glist=idlist, style="W")
range(rowSums(d75MAT))

w75 <- nb2listw(d75, glist=idlist, style="W")
range(sapply(w75$weights, sum))

d75MAT[1:5,1:5]

inMAT[1:5,1:5]

rowSums(inMAT[1:5,])

rowSums(d75MAT[1:5,])

I really appreciate this.  Thank you,

Terry



-----Original Message-----
From: Roger Bivand [mailto:Roger.Bivand at nhh.no] 
Sent: Friday, March 17, 2006 5:50 PM
To: Griffin, Terry W
Cc: r-sig-geo at stat.math.ethz.ch
Subject: RE: [R-sig-Geo] inverse distance weights matrix

Terry:

http://web.ics.purdue.edu/~twgriffi/mat4rf

and 

http://web.ics.purdue.edu/~twgriffi/mat4rs

throw access errors.

Do you have the coordinates and your specifications for the inverse 
weighted neighbours (distance threshold, power if any)? 

inMAT <- matrix(scan("cottonID75wm", sep=","), nrow=2451, ncol=2451, 
  byrow=TRUE)

does read the matrix - the weights aren't symmetric, are they?

From the weights matrix I get:

inMATlw <- mat2listw(inMAT)

print(is.symmetric.nb(inMATlw$neighbours))
[1] TRUE

print(inMATlw$neighbours)
Neighbour list object:
Number of regions: 2451 
Number of nonzero links: 1182982 
Percentage nonzero weights: 19.69208 
Average number of links: 482.6528 

If you could post the coordinates and your specifications, I could see
how 
to reproduce the weights within R if you like.

Roger


On Fri, 17 Mar 2006, Griffin, Terry W wrote:

The MATLAB routines are the Spatial Econometrics Toolbox format.  I
tried the read.dat2listw() in R; the code and error message for a

small

matrix example is below; this uses a full matrix from MATLAB

(realizing

that "read.dat2listw" is intended for sparse matrices). 

mattry<-read.dat2listw("mat4rf")

Error in "[.default"(sn, , 1) : incorrect number of dimensions

traceback()

5: NextMethod("[")
4: "[.factor"(sn, , 1)
3: sn[, 1]
2: unique(sn[, 1])
1: read.dat2listw("mat4rf")


I'm not able to use dlmwrite in MATLAB to export the sparse matrix so

I

tried to import the full matrix into R (code is above).  The MATLAB

code

I'm using came from this listserve archive.  The MATLAB code and error
message are below.  I'm able to use dlmwrite to create the MATLAB full
matrix (used above in the R code).

load testmat.GWT; A = (spconvert(testmat)); %have to change name in

two

locations on this line
n=size(A); nobs=n(1);
 % Normalize matrix (adapted form LeSage 1999)
wt = sparse(A);
 [i1,j1,s1]=find(wt);
rsum=sum(wt);
for i=1:nobs;
            ind=find(i1==i);
s1(ind,1)=s1(ind,1)/rsum(1,i);
end;
[m,n] = size(wt);
W = sparse(i1,j1,s1,m,n);
S = sparse(W);
dlmwrite('mat4rst', S); %give the new sparse weight matrix a permanent
name for R 
??? Error using ==> sprintf
Function is not defined for sparse inputs.

Error in ==> dlmwrite at 172
        str = sprintf(format,m(i,:));

If anyone wants to give it a try, I've put the small example matrices
and the "real" matrix up on my website at:
http://web.ics.purdue.edu/~twgriffi/R_matrix.htm

My objective is to use R for my spatial data analysis using inverse
distance weights matrices.  I'm struggling with the inverse distance
matrices.  I hope to either create these inverse distance matrices in
SpaceStat then import into R or create the matrices in R.  

Thank you,

Terry




-----Original Message-----
From: Roger Bivand [mailto:Roger.Bivand at nhh.no] 
Sent: Friday, March 17, 2006 2:43 PM
To: Griffin, Terry W
Cc: r-sig-geo at stat.math.ethz.ch
Subject: Re: [R-sig-Geo] inverse distance weights matrix

On Thu, 16 Mar 2006, Griffin, Terry W wrote:

Greetings,

 

I'm migrating from MATLAB to R and am having trouble converting

inverse

distance weights matrix into a form usable by R.  I've created the
matrix in SpaceStat (in *.FMT format) and converted to *.GWT format

and

also have it in MATLAB *.m format.

I wonder whether your Matlab data are in the Spatial Econometrics
Toolbox 
format - if they are, you could try the read.dat2listw() function 
mentioned on the read.gwt2nb function help page.

 

I've tried using the read.gwt2nb in R, but without success.  There

are

nearly 2,451 observations with an average of 482 linkages.  About 20

%

have nonzero weights.  Any suggestions are appreciated.

Without details of what you mean by "without success", it's hard to
offer 
any advice. Could you create a small example of the problems you are 
seeing, and repost with copies of the commands you give and any error 
messages? 

If you are seeing errors ("Error in ..." messages from R), please also
type traceback() at the prompt and report the output. You could also

put

the uncooperative GWT file on a website for others to try to see what

is

going on.

 

Thank you,

Terry

 

 

Terry W. Griffin

Graduate Research Assistant

Agricultural Economics

Purdue University

403 W State St

West Lafayette, IN 47907

765-494-4257

http://web.ics.purdue.edu/~twgriffi/
<http://web.ics.purdue.edu/~twgriffi/> 

 

 


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