assign15 - Assignment 15 Geographically Weighted Regression...

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1 Assignment 15. Geographically Weighted Regression & 2D Mapping I: Formatting Data for the Stand-Alone GWR Program § Here’s an example using U.S. Census data. § In the GWR stand-alone program, create folders for ‘Data,’ ‘Output,’ and ‘Models.’ § Obtain a census tract shapefile and a tract socio-demographic layer. o In ArcCatalog set a coordinate system for the shapefile. o Of course, instead of census tract data you could use block group data or block data. § U.S. Census block group and block data have more spatial units than tract data and so will considerably slow down the GWR program. § Whether or not a particular data set represents a random sample has serious implications for the statistical analysis of the GWR output. § In ArcMap, set the coordinate system and to store relative paths. § Add the shapefile and sociodemographic layer to ArcMap. § In ArcMap, table join the two layers, selecting from the state-level data the spatial unit (e.g., Orleans Parish) that you intend to analyze by clicking ‘Advanced’ and specifying ‘Keep only matching files.’ § Export and save the table join as a new layer, and undo the original table join. § In the new layer, create X and Y centroid fields, and create the variables you intend to analyze in GWR. § Do exploratory analysis to identify and eliminate spatial units (e.g., units with no or sparse population; extreme outlier units in other respects) that could distort the GWR results. o If you eliminate spatial units at this stage, you may ultimately want to map the reduced-size shapefile together with the original shapefile, symbolizing the eliminated units as, e.g., “Not Analyzed.” o See the notes on how to do so at the end of this assignment documentt. § Use Excel, Stata, SPSS, or other statistical program to delete unnecessary fields. In general, keep STFID (or some ID field without text), X and Y centroids, and the variables (without text) that you intend to analyze. o Double-check to make sure that the ID field, etc., is correct. § E.g., statistical programs such as Stata may unsort the ID-variable, which has to be resorted before saving the data for use in GWR and ArcMap. o Do not include any field/variable that contains text. E.g., include STFID but not GEO_ID, because GEO_ID contains text. § Use Excel to save this streamlined data with a .csv extension in GWR’s ‘Data’ folder. o It seems that Excel, but not StatTransfer, should be used to do this.
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2 II. Running a GWR Model § The following assumes that you’ve performed exploratory analysis and made required adjustments for outliers and so on. o Make sure to check the data for possible errors (e.g., sum categorical series of fields to make sure that they add up to the appropriate totals). § We’ll use ‘GeorgiaData.csv’ (see Fotheringham et al., chapter 9).
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This note was uploaded on 07/11/2011 for the course SYA 6356 taught by Professor Staff during the Spring '08 term at University of Florida.

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assign15 - Assignment 15 Geographically Weighted Regression...

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