Default panel function for dotplot.
panel.dotplot(x, y, horizontal = TRUE,
              pch, col, lty, lwd, 
              col.line, levels.fos,
              groups = NULL,
              …,
              identifier = "dotplot")variables to be plotted in the panel. Typically y is the ‘factor’
logical. If FALSE, the plot is ‘transposed’
    in the sense that the behaviours of x and y are switched. x is now
    the ‘factor’.  Interpretation of other arguments change
    accordingly. See documentation of bwplot for a fuller
    explanation.
graphical parameters
locations where reference lines will be drawn
grouping variable (affects graphical parameters)
extra parameters, passed to panel.xyplot which is responsible
    for drawing the foreground points (panel.dotplot only draws
    the background reference lines).
A character string that is prepended to the names of grobs that are created by this panel function.
Creates (possibly grouped) Dotplot of x against y or
  vice versa