[R-sig-Geo] error in errorsarlm

[Roger Bivand]

On Fri, 23 Jul 2010, elaine kuo wrote:

>>
>>
>>>>> 1. change method to Matrix
>>>
>>>
>>>  System calculation is specific, the condition is =5.14146e-17 (translated
>>> from Chinese)
>>>
>>> Warning messages:
>>>
>>
>> Warning not a problem, but the error suggests scaling problems in the
>> covariance matrix of the coefficients. The X variables are most likely
>> measured in inappropriate metrics (some coefficients of size 1000, others of
>> size 0.0001, for example).
>>
>> ==>  using standardized regression, the warning disappeared as you advised.
>>
>
>  However, another set of warning appears:
>
>  Warning messages:
> 1: In determinant(x, TRUE) : This version of the Matrix package returns
> |determinant(L)| instead of determinant(A), i.e., a
> *DIFFERENT* value.
> If still necessary, do change your code, following
> http://matrix.r-forge.r-project.org
>
> 2: In powerWeights(W = W, rho = lambda, order = con$pWOrder, X = B,  :
>  not converged within order iterations
> 3: In powerWeights(W = t(W), rho = lambda, order = con$pWOrder, X = C,  :
>  not converged within order iterations
>
> Please kindly advise how to modify the code below from determinant L to
> determinant A and why ?

The warning is irrelevant. The error is caused by your weights.

>
>
> 2. great distance circle
>
> And make sure that you do use Great Circle distances - you are not doing so
> now.
> With 200 neighbours, you have no viable spatial process, really.
>
> => longlat = TRUE returns no valid observation ...
>     similar error messages have been researched in the archived mail
>     but no identical case found...
>    Please kindly suggest when longlat=TRUE,
>    whether the unit of both longitude and latitude is degree.decimal..
>    (confused with the manual explanation "measured in kilometer")

The threshold is in km when longlat=TRUE, but the coordinates are in 
decimal degrees. Please state the representation of your coordinates - are 
they in decimal degrees or not?

>
>    Also, does "no viable spatial process" mean
>   no spatial interaction within the range should be taken into
> consideration ?

No, simply that you are including too many neighbours leading to too much 
smoothing for many observations.

Please try everything on small examples until you understand what you are 
doing. Best, use publically available small examples, and include complete 
verbatim code (or post code on a website), max. 10 lines.


>
>   Thank you
>
>   Elaine
>
>
> code
> datam <-read.csv("c:/migration/M_R_SummerM20100722.csv",header=T,
> row.names=1)
>
> # std method   scale
>  datam.sd<-scale(datam)
>  datam.std<-as.data.frame(datam.sd)
>  summary (datam.std)
>  mean(datam.std)
>
>  # obtain standard deviation
>  sd(datam.std)
>
>  mig.std
> <-lm(datam.std$SummerM_ratio~datam.std$coast+datam.std$topo_mean+datam.std$prec_mean+datam.std$temp_ran+datam.std$evi_ran,data=datam.std)
>  summary(mig.std)
>
>  #SAR
>
>  library(ncf)
>  library(spdep)
>
>  # Define coordinates, neighbours, and spatial weights
>  coords<-cbind(datam$lon,datam$lat)
>  coords<-as.matrix(coords)
>
>  #Define neighbourhood (here distance 5)
>  nb5<-dnearneigh(coords,0,5,longlat=TRUE)
>
>
>  #Spatial weights, illustrated with coding style "W" (row standardized)
>  nb5.w<-nb2listw(nb5, glist=NULL, style="W", zero.policy=TRUE)
>
>
>   +++error in nb2listw(nb5, glist = NULL, style = "W", zero.policy = TRUE)
> :
>  No valid observations  +++
>  (then modified as  nb5<-dnearneigh(coords,0,5) and Matrix went on
> smoothly )
>
>  # Spatial SAR error model
>  sem.nb5.w <-
> errorsarlm(datam.std$SummerM_ratio~datam.std$coast+datam.std$topo_mean+datam.std$prec_mean+datam.std$temp_ran+datam.std$evi_ran,data=datam.std,
> listw=nb5.w, na.action=na.omit, method="Matrix", zero.policy=TRUE)
>
>
>
>>
>>
>> +++warning
>>
>>
>>> 1: In determinant(x, TRUE) : This version of the Matrix package returns
>>>
>>> |determinant(L)| instead of determinant(A), i.e., a
>>>
>>> *DIFFERENT* value.
>>>
>>> If still necessary, do change your code, following
>>> http://matrix.r-forge.r-project.org
>>>
>>>
>>>
>>> 2: In powerWeights(W = W, rho = lambda, order = con$pWOrder, X = B,  :
>>>
>>>  not converged within order iterations
>>>
>>> 3: In powerWeights(W = t(W), rho = lambda, order = con$pWOrder, X = C,  :
>>>
>>>  not converged within order iterations  ++++
>>>
>>>
>>>
>>>
>>>
>>>
>

-- 
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