Spatially Discrete Approximation to Log-Gaussian Cox Processes for Aggregated Disease Count Data

Provides a computationally efficient discrete approximation to log-Gaussian Cox process model for spatially aggregated disease count data. It uses Monte Carlo Maximum Likelihood for model parameter estimation as proposed by Christensen (2004) and delivers prediction of spatially discrete and continuous relative risk. It performs inference for static spatial and spatio-temporal dataset. The details of the methods are provided in Johnson et al (2019) .

SDALGCP provides a computationally efficient discrete approximation to log-Gaussian Cox process (LGCP) model for spatially aggregated disease count data. It uses Monte Carlo Maximum Likelihood for model parameter estimation and delivers prediction of spatially discrete and continuous relative risk.

Installation

To install the latest development of SDALGCP package use

Example

Here I present an illustrative example of how to use the package

extract the dataframe containing data from the object loaded

set any population density that is NA to zero

write a formula of the model you want to fit

Now to proceed to fitting the model, note that there two types of model that can be fitted. One is when approximate the intensity of LGCP by taking the population weighted average and the other is by taking the simple average. We shall consider both cases in this tutorial, starting with population weighted since we have population density on a raster grid of 300m by 300m.

SDALGCP I (population weighted)

Here we estimate the parameters of the model

Discretise the value of scale parameter ϕ

estimate the parameter using MCML

To print the summary of the parameter estimates as well as the confidence interval, use;

We create a function to compute the confidence interval of the scale parameter using the deviance method. It also provides the deviance plot.

Having estimated the parameters of the model, one might be interested in area-level inference or spatially continuous inference.

1. If interested in STRICTLY area-level inference use the code below. This can either give either region-specific covariate-adjusted relative risk or region-specific incidence. This is achieved by simply setting in the function.

From this discrete inference one can map either the region-specific incidence or the covariate adjusted relative risk.

1. If interested in spatially continuous prediction of the covariate adjusted relative risk. This is achieved by simply setting in the function.

Then we map the spatially continuous covariate adjusted relative risk.

SDALGCP II (Unweighted)

As for the unweighted which is typically by taking the simple average of the intensity an LGCP model, the entire code in the weighted can be used by just setting in the line below.

Spatio-temporal SDALGCP

create a spacetime object as an input of the spatio-temporal SDALGCP model

Plot the spatio-temporal count data

Parameter estimation

Area-level of the spatio-temporal prediction

Ploting the area-level incidence and the covariate adjusted relative risk

Spatially continuous prediction of the covariate adjusted relative risk

Ploting the spatially continuous covariate-adjusted relative risk

mypackage 0.2.0

These are the improvements in these version.

Major changes

• provides a spatio-temporal extension of the model
• provides an option to include a base map

Bug fixes

• fix the bug with method
• remove the pbapply function and use progress

mypackage 0.1.0

This is the first release to Cran.

Reference manual

install.packages("SDALGCP")

0.4.0 by Olatunji Johnson, 10 months ago

Browse source code at https://github.com/cran/SDALGCP

Authors: Olatunji Johnson [aut, cre] , Emanuele Giorgi [aut] , Peter Diggle [aut]

Documentation:   PDF Manual