

_C_o_n_d_i_t_i_o_n_i_n_g _P_l_o_t_s

     coplot(formula, data, given.values, panel = points, rows, columns,
            show.given = TRUE, col = par("fg"), pch = par("pch"), ...)
     co.intervals(x, number = 6, overlap = 0.5)

_A_r_g_u_m_e_n_t_s:

 formula: a formula describing the form of conditioning
          plot.  A formula of the form `y ~ x | a' indicates
          that plots of `y' versus `x' should be produced
          conditional on the variable `a'.  A formula of the
          form `y ~ x| a * b' indicates that plots of `y'
          versus `x' should be produced conditional on the
          two variables `a' and `b'.

          `x' and `y' must be numeric, but `a' and `b' may
          be either numeric or factors.

    data: a data frame containing values for any variables
          in the formula.  By default the environment where
          `coplot' was called from is used.

given.values: a value or list of two values which determine
          how the conditioning on `a' and `b' is to take
          place.  Usually this is a matrix with two columns
          each row of which gives an interval, to be condi-
          tioned on, but is can also be a single vector of
          numbers or a set of factor levels (if the variable
          being conditioned on is a factor).

          The result of `co.intervals(..)' can be used
          directly as `given.values' argument.

   panel: a function which gives the action to be carried
          out in each panel of the display.  The default is
          `points'.

    rows: the panels of the plot are laid out in a `rows' by
          `columns' array.  `rows' gives the number of rows
          in the array.

 columns: the number of columns in the panel layout array.

show.given: should conditioning plots be shown for the con-
          ditioning variables (default `TRUE')

     col: a vector of colors to be used to plot the points.
          If too short, the values are recycled.

     pch: a vector of plotting symbols or characters.  If
          too short, the values are recycyled.

     ...: additional arguments to the panel function.

  number: the number conditioning intervals.

 overlap: the fraction of overlap of the conditioning vari-
          ables.

_D_e_s_c_r_i_p_t_i_o_n:

     This function produces two variants of the conditioning
     plots discussed in the reference below.

_R_e_f_e_r_e_n_c_e_s:

     Cleveland, W. S. (1993).  Visualizing Data.  New Jer-
     sey: Summit Press.

_S_e_e _A_l_s_o:

     `pairs', `panel.smooth', `points'.

_E_x_a_m_p_l_e_s:

     ## Tonga Trench Earthquakes
     data(quakes)
     coplot(long ~ lat | depth, data = quakes)
     coplot(long ~ lat | depth * mag, data = quakes)

