R: Support for MCMC-based estimation

as.mcmc.emmGrid {emmeans} | R Documentation

## Support for MCMC-based estimation

### Description

When a model is fitted using Markov chain Monte Carlo (MCMC) methods, its reference grid contains a `post.beta` slot. These functions transform those posterior samples to posterior samples of EMMs or related contrasts. They can then be summarized or plotted using, e.g., functions in the coda package.

### Usage

    ## S3 method for class 'emmGrid'
    as.mcmc(x, names = TRUE, sep.chains = TRUE, ...)

    ## S3 method for class 'emmGrid'
    as.mcmc.list(x, names = TRUE, ...)

### Arguments

`x` | An object of class `emmGrid`
`names` | Logical scalar or vector specifying whether variable names are appended to levels in the column labels for the `as.mcmc` or `as.mcmc.list` result – e.g., column names of `treat A` and `treat B` versus just `A` and `B`. When there is more than one variable involved, the elements of `names` are used cyclically.
`sep.chains` | Logical value. If `TRUE`, and there is more than one MCMC chain available, an `mcmc.list` object is returned by `as.mcmc`, with separate EMMs posteriors in each chain.
`...` | (Required but ignored)

### Value

An object of class `mcmc` or `mcmc.list`.

### Details

When the object's `post.beta` slot is non-trivial, `as.mcmc` will return an `mcmc` or `mcmc.list` object that can be summarized or plotted using methods in the coda package. In these functions, `post.beta` is transformed by post-multiplying it by `t(linfct)`, creating a sample from the posterior distribution of LS means. In `as.mcmc`, if `sep.chains` is `TRUE` and there is in fact more than one chain, an `mcmc.list` is returned with each chain's results. The `as.mcmc.list` method is guaranteed to return an `mcmc.list`, even if it comprises just one chain.

[Package emmeans version 1.1.3 Index]