error using predict.sarlm

Hi Roger,

Then the dak_test_data is a SpatialPolygonsDataFrame, for which there is 
no nrow() method, leading to problems. Please get around this by saying 
newdata=as(dak_test_data, "data.frame") to coerce it to data frame. I'll 
look at providing dim methods for Spatial*DataFrame objects other than 
SpatialPointsDataFrame, which are in sp already; nrow() just returns 
dim()[1] of the object.

Thanks for your help so far. I tried your suggestion using the following 
code:

dak_test_vars.10nn.predict <- predict.sarlm(reg_vars_formula.lag, 
newdata=as(dak_test_vars, "data.frame"), listw = 
dak_test.10nn.listw,zero.policy=TRUE)

Now I get a new error message: "Error in invIrW(listw, object$rho) %*% 
trend : non-conformable arguments". I double checked the listw object and 
data frame properties. They are as follows:

nrow(as(dak_test_vars, "data.frame") = 2255
length(dak_test.10nn.listw)
[1] 3
names(dak_test.10nn.listw)
[1] "style"      "neighbours" "weights"   
length(dak_test.10nn.listw[[2]])
[1] 2255
length(coords_test)
[1] 4510

I am unsure of how to interpret this error. Do you have any advice? Thanks 
for your help.

Heather

Heather Sander
Ph.D. Candidate:  Conservation Biology
Office:  305 Ecology & 420 Blegen
Mail:  
University of Minnesota
Dept. of Geography
414 Social Science Bldg.
267 19th Ave. S.
Minneapolis, MN 55455
USA