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From | "P. Wilner Jeanty" <pwjeanty@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | st: New version of -spmlreg- and -spwmatrix- available on SSC |
Date | Wed, 19 Mar 2014 12:35:53 -0400 |
Thanks to Kit Baum, -spmlreg- and -spwmatrix- have been updated on SSC. Here are some features of the new version of -spwmatrix-: 1) Users can now import into Stata spatial weights created in both ArcGIS and GeoDa. For example, you might want to generate a Delaunay Triangle spatial weights matrix in ArcGIS and import it into Stata to conduct the spatial analysis. The help file for -spwmatrix- contains links to ArcGIS resource center that would show how to create a spatial weights matrix and prepare it for import. 2) Spatial weights created and imported in Stata can be exported for use in Matlab and R by specifying the -xport()- option like xport(wghtmatrixname, dat). 3) Created and imported spatial weights can be used with the -spivreg- command by Drukker et al. using either the -external- or -mataf- option. For instance, if you specify the -external- option, you can create an -spmat- object to be used with -spivreg- by coding: . spmat putmatrix newspwgt spwgt, id(idvarname) In the code above, spwgt is the name of the spatial weights matrix previously created by -spwmatrix- and newspwght is the name of the -spmat- object to be created for use with -spivreg- (or -spreg-,- xsmle- for that matter). -idvarname- is the name of your id variable. If you don't have one, you can create it by coding: . gen idvarname=_n 4) Using the -xtw(#)- option, users can now generate spatial weights for a balanced panel dataset. For example, you might want to generate spatial weights for use with -splagvar- in order to generate spatially lagged variables in a panel data context. Below are some suggestions how to do that. a) Sort your data by year and areal unit - crucial in spatial panel data analysis . sort year panelid b) Generate the spatial weights matrix for a single year. It does not matter which year you choose from your dataset since you will have the same results. For example, you could type: . spwmatrix gecon latitude longitude if year==2000, wname(spw_panel) wtype(inv) alpha(2) row mataf xtw(20) dband(0,1000) // just an example The key option here is xtw(20), where 20 is the number of years in your dataset. c) Now give a call to -splagvar- to generate spatially lagged variables. . splagvar depvar, wname(spw_panel) wfrom(Mata) ind(indepvars) other_options // Here I use -wfrom(Mata)- since I specified the -mataf- option when creating the weights matrix.