level.colors             package:lattice             R Documentation

_A _f_u_n_c_t_i_o_n _t_o _c_o_m_p_u_t_e _f_a_l_s_e _c_o_l_o_r_s _r_e_p_r_e_s_e_n_t_i_n_g _a _n_u_m_e_r_i_c _o_r
_c_a_t_e_g_o_r_i_c_a_l _v_a_r_i_a_b_l_e

_D_e_s_c_r_i_p_t_i_o_n:

     Calculates false colors from a numeric variable (including
     factors, using their numeric codes) given a color scheme and
     breakpoints.

_U_s_a_g_e:

     level.colors(x, at, col.regions, colors = TRUE, ...)

_A_r_g_u_m_e_n_t_s:

       x: A numeric or 'factor' variable. 

      at: A numeric variable of breakpoints defining intervals along
          the range of 'x'. 

col.regions: A specification of the colors to be assigned to each
          interval defined by 'at'.  This could be either a vector of
          colors, or a function that produces a vector of colors when
          called with a single argument giving the number of colors.  
          See details below. 

  colors: logical indicating whether colors should be computed and
          returned.  If 'FALSE', only the indices representing which
          interval (among those defined by 'at') each value in 'x'
          falls into is returned.  

     ...: Extra arguments, ignored. 

_D_e_t_a_i_l_s:

     If 'at' has length n, then it defines n-1 intervals.  Values of
     'x' outside the range of 'at' are not assigned to an interval, and
     the return value is 'NA' for such values.

     Colors are chosen by assigning a color to each of the n-1
     intervals. If 'col.regions' is a palette function (such as
     'topo.colors', or the result of calling 'colorRampPalette'), it is
     called with n-1 as an argument to obtain the colors.  Otherwise,
     if there are exactly n-1 colors in 'col.regions', these get
     assigned to the intervals.  If there are fewer than n-1 colors,
     'col.regions' gets recycled.  If there are more, a more or less
     equally spaced (along the length of 'col.regions') subset is
     chosen.

_V_a_l_u_e:

     A vector of the same length as 'x'.  Depending on the 'colors'
     argument, this could be either a vector of colors (in a form
     usable by R), or a vector of integer indices representing which
     interval the values of 'x' fall in.

_A_u_t_h_o_r(_s):

     Deepayan Sarkar deepayan.sarkar@r-project.org

_S_e_e _A_l_s_o:

     'levelplot', 'colorRampPalette'.

_E_x_a_m_p_l_e_s:

     depth.col <-
         with(quakes, 
              level.colors(depth, at = do.breaks(range(depth), 30),
                           col.regions = terrain.colors))

     xyplot(lat ~ long | equal.count(stations), quakes,
            strip = strip.custom(var.name = "Stations"),
            colours = depth.col,
            panel = function(x, y, colours, subscripts, ...) {
                panel.xyplot(x, y, pch = 21, col = "transparent",
                             fill = colours[subscripts], ...)
            })

