# testlik.fun: Likelihood ratio test to compare two nested models In NHPoisson: Modelling and Validation of Non Homogeneous Poisson Processes

## Description

This function performs a likelihood ratio test, a test to compare the fit of two models, where the first one (the null model ModR) is a particular case of the other (the alternative model ModG).

## Usage

 1  testlik.fun(ModG, ModR) 

## Arguments

 ModG An object of class mlePP-class; usually, the output from fitPP.fun. ModR An object of class mlePP-class; usually, the output from fitPP.fun.

## Details

The test statistic is twice the difference in the log-likelihoods of the models. Under the null, the statistic follows a χ^2 distribution with degrees of freedom df2-df1,the number of parameters of modG and modR respectively.

## Value

A list with elements

 pv P-value of the likelihood ratio test. ModG Input argument. ModR Input argument.

## References

Casella, G. and Berger, R.L., (2002). Statistical inference. Brooks/Cole.

fitPP.fun,LRTpv.fun
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 ##The alternative model modB is specified by the output fitPP.fun ##The null model modBR is specified by a list with elments llik and npar data(BarTxTn) covB<-cbind(cos(2*pi*BarTxTn$dia/365), sin(2*pi*BarTxTn$dia/365), BarTxTn$TTx,BarTxTn$Txm31,BarTxTn$Txm31**2) modB<-fitPP.fun(tind=TRUE,covariates=covB, POTob=list(T=BarTxTn$Tx, thres=318), tim=c(1:8415), tit="BAR Tx; cos, sin, TTx, Txm31, Txm31**2", start=list(b0=-100,b1=1,b2=10,b3=0,b4=0,b5=0),dplot=FALSE,modCI=TRUE, modSim=TRUE) modBR<-fitPP.fun(tind=TRUE,covariates=covB[,1:4], POTob=list(T=BarTxTn\$Tx, thres=318), tim=c(1:8415), tit="BAR Tx; cos, sin, TTx, Txm31", start=list(b0=-100,b1=1,b2=10,b3=0,b4=0),dplot=FALSE,modCI=TRUE, modSim=TRUE) aux<-testlik.fun(ModG=modB,ModR=modBR)