TRUE/FALSE to turn free y scales on the facetted plots on or off (default FALSE). Only works if facet = TRUE.
strip
Number indicating which column to strip off (i.e., strip=1 removes first column, which is necessary for most MCMC outputs in which the first column is just the generation).
You can skip multiple columns by passing a vector of columns to skip, e.g., strip=c(1,4,6).