R: Burn-in

burnin {LaplacesDemon} | R Documentation

## Burn-in

### Description

The `burnin` function estimates the duration of burn-in in iterations for one or more Markov chains. “Burn-in” refers to the initial portion of a Markov chain that is not stationary and is still affected by its initial value.

### Usage

    burnin(x, method="BMK")

### Arguments

`x` | This is a vector or matrix of posterior samples for which a the number of burn-in iterations will be estimated.
`method` | This argument defaults to `"BMK"`, in which case stationarity is estimated with the `BMK.Diagnostic` function. Alternatively, the `Geweke.Diagnostic` function may be used when `method="Geweke"` or the `KS.Diagnostic` function may be used when `method="KS"`.

### Details

Burn-in is a colloquial term for the initial iterations in a Markov chain prior to its convergence to the target distribution. During burn-in, the chain is not considered to have “forgotten” its initial value.

Burn-in is not a theoretical part of MCMC, but its use is the norm because of the need to limit the number of posterior samples due to computer memory. If burn-in were retained rather than discarded, then more posterior samples would have to be retained. If a Markov chain starts anywhere close to the center of its target distribution, then burn-in iterations do not need to be discarded.

In the `LaplacesDemon` function, stationarity is estimated with the `BMK.Diagnostic` function on all thinned posterior samples of each chain, beginning at cumulative 10% intervals relative to the total number of samples, and the lowest number in which all chains are stationary is considered the burn-in.

The term, “burn-in”, originated in electronics regarding the initial testing of component failure at the factory to eliminate initial failures (Geyer, 2011). Although “burn-in' has been the standard term for decades, some are referring to these as “warm-up” iterations.

### Value

The `burnin` function returns a vector equal in length to the number of MCMC chains in `x`, and each element indicates the maximum iteration in burn-in.

### Author(s)

Statisticat, LLC. software@bayesian-inference.com

### References

Geyer, C.J. (2011). "Introduction to Markov Chain Monte Carlo". In S Brooks, A Gelman, G Jones, and M Xiao-Li (eds.), "Handbook of Markov Chain Monte Carlo", p. 3–48. Chapman and Hall, Boca Raton, FL.

### See Also

`BMK.Diagnostic`, `deburn`, `Geweke.Diagnostic`, `KS.Diagnostic`, and `LaplacesDemon`.

### Examples

    library(LaplacesDemon)
    x <- rnorm(1000)
    burnin(x)

[Package LaplacesDemon version 16.1.1 Index]