 Welcome
The purpose of this webpage is to make available to researchers papers and programs in my areas of interest. I try to use the tools of econometrics and GIS to research issues related to economic development and tropical deforestation. My hope is that through my research, poverty will be reduced, and the environment will be used in a sustainable and sensible way. On a more theoretical note, I hope to contribute to the growing field of spatial econometrics.
You may want to try some of my tools for working with sparse matrices in MatLab. MatLab has the unfortunate tendency to form unnecessarily large sparse matrices. For example, with a sparse W matrix at 3.2MB and 5,661 cells square, we find that W*W takes up 88MB, but that has a lot of zeros -- something a sparse matrix is designed not to have. When I eliminate the zeros, it shrinks to a more reasonable 10MB. It gets worse: W*W*W is 280MB with all the extra zeros, but 20MB without them. And for W*W*W*W, the matrix is 385MB as a sparse matrix, while the full version of the matrix is 256MB, and the sparse matrix with the zeros removed is only 31MB. If we are willing to discard elements smaller that 0.000001, then the matrix shrinks further to 19MB.
The programs and documents here are provided in good faith. I try to provide programs that are useful and correct. However, there are no guarantees that these programs and papers are without errors. Many of them have not been refereed, and checking one's own work is no guarantee of correctness. If you should find any errors in the programs or papers, please email me, and I will try to repair them as best as possible. I also welcome any comments, suggestions, or discussions.
Thanks for stopping by!
Spatial econometrics
I have been working on the spatial probit for a couple of years now. I have written a program, based on the one by Jim LeSage, that handles not only the probit, but the tobit and linear model, as well. The program uses MCMC methods. It no longer requires downloading Jim's toolboxes, though I cannot imagine why anyone using MatLab would not want them. I am indebted to Jim LeSage for doing the pioneering work of generating the programs, writing correspoding textbooks, and making all of this publicly available at his website. I highly recommend downloading his textbooks, especially the spatial econometrics textbook.
A suggested citation for the notes on the spatial probit might be as follows:
Thomas, Timothy S. 2007. "A Primer for Bayesian Spatial Probits, With an Application to Deforestation in Madagascar", Companion Paper for the World Bank Policy Research Report on Forests, Environment, and Livelihoods, Washington, D.C. Downloaded from http://www.timthomas.net.
Similar citations could be used for the programs. Likewise, LeSage's Econometrics Toolbox might be cited as:
LeSage, James P. 2003. "Econometrics Toolbox", MatLab programs. Downloaded from http://www.spatial-econometrics.com.
Other Econometrics and Statistics
Amazon and Brazilian Data and Tools
More to be added soon...
Arc View Avenue scripts
Most of these Avenue scripts are based, sometimes almost completely, on scripts I downloaded from the ESRI website. I have kept the authors' names and contacts in the file headers when this is the case.
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Go to ESRI's Avenue script webpage...
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Generates an output file that lists neighbors to each polygon based on whether the polygons touch. It also comments on whether any 2 polygons overlaps, or whether one might be contained in the other one.
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Identifies gaps between polygons and attempts repair
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Identifies overlaps between polygons and attempts repair
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Converts Arc Info GEN format to shapefile (handles donut polygons)
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Converts shapefiles to Arc Info GEN files (handles donut polygons)
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Computes lengths of polylines, places in dbf file, and joins with shapefile
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Interpolates missing values of a field by averaging the non-missing values of geographic neighbors
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Computes area for polygon file that is already projected
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Computes area for polygon file in geographic projection (lat-long) by projecting it to one of 3 equal area projections
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From a given theme, makes individual polygons from multipart polygons, and writes the entire file to a new shapefile
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Creates a field which tells how many parts each polygon has.
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Takes a point shapefile with x- and y-coordinates and field containing area, and converts to square or circle shapefile with centroids of the points and areas given by the field
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Computes centroids for each polygon and creates a new point shapefile. If the centroid is external to the polygon, moves the centroid to the nearest point of the polygon.
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Given a point shapefile, reads field values from geographically corresponding polygons in polygon shapefile
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Given a grid, reads field values from geographically corresponding grids using the ArcView SAMPLE command
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Reads field values from geographically corresponding values of grids using points from a point shapefile
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Adds X and Y coordinates of features to Attribute Table
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Converts a gridfile into a point shapefile
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Converts a gridfile into a polygon shapefile of squares the same size as gridcells
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Generates a farmgate price grid, given a friction grid and a pointfile containing market prices and locations. This program can be very slow, because it generates a price grid for every market, the computes the maximum price at each gridcell. Nevertheless, this is quite a powerful tool for realworld farmgate price calculations.
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Merges several grids together
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Computes minimum value at each gridcell given a collection of grids
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Sums values at each gridcell given a collection of grids
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For a user-specified field, checks to see if values are unique for each shape (row, observation)
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Makes a new field, and numbers each shape consecutively, to create a unique id code
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Converts a file with lat-long in seconds to a file with lat-long in decimal degrees.
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Renames a field
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Some polygon files erroneously have holes not cut out, but listed as separate polygons. This takes those polygons, and cuts the holes out.
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Unions all polygons in a theme, making one big polygon
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Geographically cuts all elements of one theme out of another theme.
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Makes a rectangle twice the size of the bounding rectangle for the theme
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Deforestation and Other Research
More to be added soon...
Dissertation
Completed July 29, 2003
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Dissertation on Roads and Amazon Deforestation (2.7 MB pdf)
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Dissertation, text only (0.5 MB pdf)
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Dissertation, figures 1 to 17 only (1.1 MB pdf)
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Dissertation, figures 18 to 29 only (1.2 MB pdf)
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Dissertation, figures 1 to 3 only, large (1.6 MB pdf)
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Dissertation, figures 4 to 6 only, large (1.8 MB pdf)
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Dissertation, figures 7 to 20 only, large (1.4 MB pdf)
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Dissertation, figures 21 to 24 only, large (1.5 MB pdf)
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Dissertation, figures 25 to 29 only, large (0.7 MB pdf)
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