window.mcmc is a method for mcmc objects which is
normally called by the generic function window In addition to the generic parameters, start and end
the additional parameter thin may be used to thin out the
Markov chain. Setting thin=k selects every kth iteration starting
with the first. Note that the value of thin is absolute
not relative. The value supplied given to the parameter thin
must be a multiple of thin(x).
Values of start, end and thin which are inconsistent
with x are ignored, but a warning message is issued.
## S3 method for class 'mcmc':
window(x, start, end, thin, \dots)window, thin.