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Pre-conference Training MCH Epidemiology – CityMatCH Joint 2012 Annual Meeting Intermediate/Advanced Spatial Analysis Techniques for the Analysis of MCH Data Tuesday, December 11, 2012. 1. Session Leaders. Russell S. Kirby, PhD, MS, FACE
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Pre-conference Training MCH Epidemiology – CityMatCH Joint 2012 Annual Meeting Intermediate/Advanced Spatial Analysis Techniques for the Analysis of MCH Data Tuesday, December 11, 2012 1
Session Leaders Russell S. Kirby, PhD, MS, FACE Department of Community and Family Health, College of Public Health, University of South Florida Marilyn O’Hara, PhD Director of GIS and Spatial Analysis Lab Department of Pathobiology University of Illinois
Topics*slide needs updating Overview Point Pattern Analysis Hot Spots Surface of Hot Spots Applications Regression Analysis Ordinary Least Squares (OLS) Geographically Weighted Regression (GWR) Testing for Spatial Autocorrelation (Moran’s I) Applications Smoothing Rates: GeoDa
Acknowledgement: This presentation based on a Powerpoint lecture by Professor Dante Verme, George Washington University
GIS • Integrates databases, graphics with digital maps. • Geographic display of information
Hot Spot Analysis • Identify Statistical Significant Spatial clusters of high (hot) or low (cold) from a particular event (areas of high counts from an event). • It works with number of events summarized in a point. • Based on the Getis-Ord test statistic
Hot Spot Analysis • Hot Spot tool is located in the Mapping Clusters toolset in the Spatial Statistics tools.
Hot Spot Analysis • To work properly it would require as input a feature class from a geodatabase. Populate its dialog.
Hot Spot Analysis Distance Bands Between Neighbor Counts Illustration
Spatial Regression • Regression: Regression establishes a relationship among a dependent variable and a set of independent variable(s) • Purpose: better understand patterns of spatial relationships between attributes. • Objective: predictions
Spatial Regression • Multiple Regression Model
Spatial Regression • Usually follows hot-spot analysis
Spatial Regression • Spatially Join the 911 Calls in Portland to a census tract layer to determine how many calls were made from each tract. • Why? Demo and SES information is available.
Spatial Regression • A spatial ordinary least square (OLS) regression model is going to determine if the number of 911 calls (dependent variable) from a Portland, OR, census track is a function of the population in each tract (independent variable).
Spatial Regression • Thematic Map of Residuals
Spatial (OLS) Regression • Moran’s Test for Residual Spatial Autocorrelation • We would like the residuals to be randomly distributed over the study area
Spatial Regression • What to do next? • Identify more predictors to be included in the model. Could be done graphically. • Generate a scatter plot matrix. Check next two slides.
Spatial Regression • What to do next? Identify more predictors to be included in the model. Generate a matrix scatterplot.
Source: Yu and Wei, Geography Department UW Simpson’s paradox Spatially aggregated data Spatially disaggregated data House Price House density House density
GWR • Associations vary spatially and are not fixed. • GWR constructs separate equations by including the dependent and explanatory variables of features that are within the bandwidth of each target feature. • Bandwiths are preferable chosen to be adaptive. • It generates a local regression model for each feature. It is truly a spatial analytical technique.
OLS vs GWR GLOBAL Model LOCAL Model
Source: Yu and Wei, Geography Department UW Fixed weighting scheme Weighting function Bandwidth
Source: Yu and Wei, Geography Department UW Adaptive weighting schemes Weighting function Bandwidth
Weighting Scheme II • dij= distance between two features i and j • hi= nearest neighbor distance from feature i