This is the default panel function for stripplot. Also see
  panel.superpose
panel.stripplot(x, y, jitter.data = FALSE,
                factor = 0.5, amount = NULL,
                horizontal = TRUE, groups = NULL,
                ...,
                grid = lattice.getOption("default.args")$grid,
                identifier = "stripplot")
coordinates of points to be plotted
whether points should be jittered to avoid
    overplotting.  The actual jittering is performed inside
    panel.xyplot, using its jitter.x or
      jitter.y argument (depending on the value of
      horizontal).
amount of jittering, see jitter
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.
optional grouping variable
additional arguments, passed on to
    panel.xyplot
A logical flag, character string, or list specifying whether and how
    a background grid should be drawn.  In its general form, grid
    can be a list of arguments to be supplied to
    panel.grid, which is called with those arguments.
    Three shortcuts are available:
TRUE:roughly equivalent to list(h = -1, v = -1)
"h":roughly equivalent to list(h = -1, v = 0)
"v":roughly equivalent to list(h = 0, v = -1)
No grid is drawn if grid = FALSE.
A character string that is prepended to the names of grobs that are created by this panel function.
Deepayan Sarkar Deepayan.Sarkar@R-project.org
Creates stripplot (one dimensional scatterplot) of x
  for each level of y (or vice versa, depending on the value of
  horizontal)