# lognormalEB: Empirical Bayes Smoothing Using a log-Normal Model In DCluster: Functions for the Detection of Spatial Clusters of Diseases

## Description

Smooth relative risks from a set of expected and observed number of cases using a log-Normal model as proposed by Clayton and Kaldor (1987). There are estimated by betatilde_i =log((O_i+1/2)/E_i) in order to prevent taking the logarithm of zero.

If this case, the log-relative risks are assumed be independant and to have a normal distribution with mean \varphi and variance sigma2. Clayton y Kaldor (1987) use the EM algorithm to develop estimates of these two parameters which are used to compute the Empirical Bayes estimate of b_i. The formula is not listed here, but it can be consulted in Clayton and Kaldor (1987).

## Usage

 1 lognormalEB(Observed, Expected, maxiter = 20, tol = 1e-05) 

## Arguments

 Observed Vector of observed cases. Expected Vector of expected cases. maxiter Maximum number of iterations allowed. tol Tolerance used to stop the iterative procedure.

## Value

A list of four elements:

 n Number of regions. phi Estimate of phi. sigma2 Estimate of sigma2. smthrr Vector of smoothed relative risks.

## References

Clayton, David and Kaldor, John (1987). Empirical Bayes Estimates of Age-standardized Relative Risks for Use in Disease Mapping. Biometrics 43, 671-681.

## Examples

 1 2 3 4 5 6 7 8 library(spdep) data(nc.sids) sids<-data.frame(Observed=nc.sids$SID74) sids<-cbind(sids, Expected=nc.sids$BIR74*sum(nc.sids$SID74)/sum(nc.sids$BIR74)) smth<-lognormalEB(sids$Observed, sids$Expected) 

DCluster documentation built on May 31, 2017, 4:37 a.m.