[R-sig-Geo] GWR Analysis

[Pinar Aslantas Bostan]

Dear Roger,

Maybe you can remember, last week I asked some questions about gwr  
analysis and you helped me. In order to make refresh, I want to  
summarize my problem. I am trying to make gwr analysis to predict  
precipitation distribution on a DEM. I have two datasets; first one is  
'station' consists of 225 prec. measurements and 3 independent  
variables (Z, V1, V2). The second one is 'DEM' dataset which has 31203  
# of pixels. Firstly I tried with using SPDF (SpatialPointsDataFrame)  
and obtained predicted precipitations on DEM. But when I plot the  
predicted precipitation values, I saw a lot of negative values which  
is impossible to get such a values. I thought that this was caused  
because I used point data sets (SPDF) for grid. Then I tried with  
using SGDF (SpatialGridDataFrame). At this time, gwr() resulted with  
an error message "new data matrix rows mismatch". You told me that  
'The error message is generated when the number of columns in the  
matrix of X variables is not the same in data and and fit.points.' I  
gave some information about datasets below.

> class(station)
[1] "SpatialPointsDataFrame"
attr(,"package")
[1] "sp"
> names(station)
[1] "PREC" "Z"    "V1"   "V2"
> class(dem)
[1] "SpatialGridDataFrame"
attr(,"package")
[1] "sp"
> names(dem)
[1] "Z"  "V1" "V2"

'PREC' is the observations and I want to get predictions of them on 'dem'.

I checked the str() and variables are stored in the same way.

> bw=gwr.sel(PREC~Z+V1+V2,data=station,adapt=T)
> xx1<-gwr(PREC~Z+V1+V2,station,adapt=bw,hatmatrix=TRUE)
> x1 <-gwr(PREC~Z+V1+V2,data=station,adapt=bw, fit.points = dem,  
> predict=T, se.fit=T, fittedGWRobject=xx1)
Error in gwr(PREC ~ Z + V1 + V2, data = station, adapt = bw,  
fit.points = dem,  :
   new data matrix rows mismatch


If I wrote 'predict=F' then gwr() works but gives only sum.w,  
coefficients and localR2.

I tried to run gwr() under debug but I didn't understand the output.

I really don't understand the problem and need help.

Best regards,
Pinar