These are methods for subsetting mcmc objects. You can select
iterations using the first dimension and variables using the second
dimension. Selecting iterations will return a vector or matrix, not an
mcmc object. If you want to do row-subsetting of an mcmc
object and preserve its dimensions, use the window function.
Subsetting applied to an mcmc.list object will simultaneously
affect all the parallel chains in the object.
# S3 method for mcmc
[(x,i,j, drop=missing(i))
# S3 method for mcmc.list
[(x,i,j, drop=TRUE)An mcmc object
Row to extract
Column to extract
if TRUE, the redundant dimensions are dropped