Determines the optimal span size for modgam, a spatial generalized additive model (GAM) with a two-dimensional LOESS smooth for location, by minimizing the AIC. Currently evaulates span sizes from 5% to 95% in increments of 5%.
Displays a color image map, including a legend, scale bar, and optional North arrow, showing crude or adjusted odds ratios (or linear predictors) for a grid of points. Irregular grids are allowed. Also draws contour lines for regions of signficantly increased or decreased values of the outcome variable ("clusters"), if permutation ranks are provided. Designed to display modgam objects but can be used with other model results if the modgamobj list contains the correct elements.
Take all cases and a random sample of controls from a data frame. Simple random sampling and stratified random sampling are available. For statified random sampling, strata can be defined by region, or by region and time. If no specific regions are specified then the function will create a regular grid for sampling.
Fits a crude or adjusted regression on a user-supplied grid for spatial analysis using a generalized additive model with a two-dimensional LOESS smooth for geolocation (or any other two-dimensional predictor). Includes optional permutation tests for global and local tests of the null hypothesis that the two-dimensional predictor (e.g., geolocation) is not associated with the outcome. Most applications will pass the output of this function to colormap to map the resulting odds ratios or other effect estimates.
Creates a data frame containing a rectangular grid of points to cover the range of X and Y coordinates provided in a data set, and trims the grid so that the points do not extend beyond the boundaries shown on a map.
Takes a subset of a data frame: returns rows with geolocations inside the boundaries determined by a map. If rectangle=FALSE, strict map boundaries are used. If rectangle=TRUE, a rectangular boundary is determined based on the range of X and Y coordinates for the map, along with an optional buffer.
providing 
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