RE: st: spatial weight matrix in stata

[Ajita Atreya <ajita63@hotmail.com>]

Hi Nichols,
I have installed sppack and I am planning to use spreg for spatial error and spatial lag dependence model. Before that I used spmat to create a weighting matrix based on the coordinates of the properties. I used banded form of matrix since I have huge dataset. But I am getting a warning: spatial matrix contains 5123 islands. I was not sure what that meant. Also, if somebody could tell me whether conginuity or inverse-distance matrix is appropriate that would help me a lot. I repeat that I have a panel data (more than 18000 obs)  and each observation refers to a single property sold at time t. 
Thank You Ajita

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> Date: Sun, 6 Nov 2011 11:04:01 -0500
> Subject: Re: st: spatial weight matrix in stata
> From: austinnichols@gmail.com
> To: statalist@hsphsun2.harvard.edu
>
> Ajita Atreya <ajita63@hotmail.com>:
> This is misguided advice from Yuval, who is telling you how to
> duplicate the effects of [aweight] for cell-average data (almost but
> not quite--you would have to deal with the constant term as well);
> instead you should use [aweight] (help weight) for such a model.
>
> You want spatial analysis, and -findit spatial- produces a
> bewilderingly long list. The place to start is
> . findit sppack
> and the references cited there.
>
> On Sun, Nov 6, 2011 at 5:35 AM, Yuval Arbel <yuval.arbel@gmail.com> wrote:
> > Ajita,
> >
> > Generally speaking, you need to provide stata the weights by yourself.
> >
> > If each observation in the sample is average data for each census
> > tract - you need to correct for hetheroskedasticity by multiplying
> > each observation in the square root of the population size for each
> > census tract.
> >
> > If each of your observation is not average but rather refers to
> > specific properties - you can generate regional dummy variables and
> > run -heckman-
> >
> > Finally, if your data is panel - you can use the -xtreg- command and
> > run a fixed-effect model, which is also based on regional dummies
> >
> >
> >
> > On Sat, Nov 5, 2011 at 8:02 PM, Ajita Atreya <ajita63@hotmail.com> wrote:
> >> Hi,
> >> I am trying to run spatial hedonic model. For that I need a spatial weight matrix. I have data on 24000 observations of property prices, the parcel number, lat  and long associated , census tract numbers, structural attributes, location attributes. It it possible to make a spatial weight matrix in stata for my dataset???
> >> Thank you in advance for your help
> >> Ajita
> >> *
> >> *   For searches and help try:
> >> *   http://www.stata.com/help.cgi?search
> >> *   http://www.stata.com/support/statalist/faq
> >> *   http://www.ats.ucla.edu/stat/stata/
> >>
> >
> >
> >
> > --
> > Dr. Yuval Arbel
> > School of Business
> > Carmel Academic Center
> > 4 Shaar Palmer Street, Haifa, Israel
> > e-mail: yuval.arbel@gmail.com
> >
> > *
> > *   For searches and help try:
> > *   http://www.stata.com/help.cgi?search
> > *   http://www.stata.com/support/statalist/faq
> > *   http://www.ats.ucla.edu/stat/stata/
> >
>
> *
> * For searches and help try:
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> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
 		 	   		  
*
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