R: Likelihood object for Poisson error distribution

lik_pois {ashr} | R Documentation

## Likelihood object for Poisson error distribution

### Description

Creates a likelihood object for ash for use with Poisson error distribution

### Usage

    lik_pois(y, scale = 1, link = c("identity", "log"))

### Arguments

`y` | Poisson observations.
`scale` | Scale factor for Poisson observations: y~Pois(scale*lambda).
`link` | Link function. The "identity" link directly puts unimodal prior on Poisson intensities lambda, and "log" link puts unimodal prior on log(lambda).

### Details

Suppose we have Poisson observations `y` where y_i\sim Poisson(c_iλ_i). We either put an unimodal prior g on the (scaled) intensities λ_i\sim g (by specifying `link="identity"`) or on the log intensities logit(λ_i)\sim g (by specifying `link="log"`). Either way, ASH with this Poisson likelihood function will compute the posterior mean of the intensities λ_i.

### Examples

       beta = c(rnorm(100,50,5)) # prior mode: 50
       y = rpois(100,beta) # simulate Poisson observations
       ash(rep(0,length(y)),1,lik=lik_pois(y))

[Package ashr version 2.2-54 Index]