The Journal of Statistical Software has a new manuscript up on the estimation of spatial differences in disease risk, using a package called “sparr”. You can download the manuscript for free.
Davies, T.M., Hazelton, M.L. & Marshall, J.C., 2011, sparr: Analyzing Spatial Relative Risk Using Fixed and Adaptive Kernel Density Estimation in R, Journal of Statistical Software, 39(1), pp. 1-14.
The estimation of kernel-smoothed relative risk functions is a useful approach to examining the spatial variation of disease risk. Though there exist several options for performing kernel density estimation in statistical software packages, there have been very few contributions to date that have focused on estimation of a relative risk function per se. Use of a variable or adaptive smoothing parameter for estimation of the individual densities has been shown to provide additional benefits in estimating relative risk and specific computational tools for this approach are essentially absent. Furthermore, little attention has been given to providing methods in available software for any kind of subsequent analysis with respect to an estimated risk function. To facilitate analyses in the field, the R package sparr is introduced, providing the ability to construct both fixed and adaptive kernel-smoothed densities and risk functions, identify statistically significant fluctuations in an estimated risk function through the use of asymptotic tolerance contours, and visualize these objects in flexible and attractive ways.
The key contribution here comes in the asymptotic tolerance contours. Still using bootstrapping, but the adaptive kernel allows us to estimate appropriate bandwidths from the actual data. Very cool.
There are numerous potential applications of the method other than disease mapping. One of my brilliant colleagues, for example, might benefit from the discussion in his research on retail subcenters.