On Fri, 24 Apr 2009, evans...@umn.edu wrote:
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
The lengths are OK now - the final one is just 2*2255, so the length of
all the elements in a two-column matrix.
The problem is occurring in multiplying (I - rho W)^{-1} by the product of
the newdata X values and the fitted regression coefficients - and suggests
that something else is going wrong earlier. If you know how to run
debug(), then do debug(predict.sarlm) and step through, checking the
dimensions and values of B and X used to create trend. If this sounds
scary, do:
save(reg_vars_formula.lag, dak_test_vars, dak_test.10nn.listw,
file="predict_problem.RData")
and attach the saved file to me offlist, and I'll try to see what is going
on.
Roger
I am unsure of how to interpret this error. Do you have any advice? Thanks
for your help.
Heather
--
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.biv...@nhh.no
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