character string indicating the boundary to test (default is "topl"). Possible values are "topl" (top-left), "topr" (top-right), "botl" (bottom-left), "botr" (bottom-right) or "all".
method
character string indicating computation method (default is "auto"). Possible values are "exact", "approximate" or "auto".
Value
a perm table that can be plotted directly using perm_plot()