hcl            package:grDevices            R Documentation(latin1)

_H_C_L _C_o_l_o_r _S_p_e_c_i_f_i_c_a_t_i_o_n

_D_e_s_c_r_i_p_t_i_o_n:

     Create a vector of colors from vectors specifying hue, chroma and
     luminance.

_U_s_a_g_e:

     hcl(h = 0, c = 35, l = 85, alpha, fixup = TRUE)

_A_r_g_u_m_e_n_t_s:

       h: The hue of the color specified as an angle in the range
          [0,360].  0 yields red, 120 yields green 240 yields blue,
          etc.

       c: The chroma of the color.  The upper bound for chroma depends
          on hue and luminance.

       l: A value in the range [0,100] giving the luminance of the
          colour.  For a given combination of hue and chroma, only a
          subset of this range is possible.

   alpha: numeric vector of values in the range '[0,1]' for alpha
          transparency channel (0 means transparent and 1 means
          opaque).

   fixup: a logical value which indicates whether the resulting RGB
          values should be corrected to ensure that a real color
          results. if 'fixup' is 'FALSE' RGB components lying outside
          the range [0,1] will result in an 'NA' value.

_D_e_t_a_i_l_s:

     This function corresponds to polar coordinates in the CIE-LUV
     color space. Steps of equal size in this space correspond to
     approximately equal perceptual changes in color.  Thus, 'hcl' can
     be thought of as a perceptually based version of 'hsv'.

     The function is primarily intended as a way of computing colors
     for filling areas in plots where area corresponds to a numerical
     value (pie charts, bar charts, mosaic plots, histograms, etc). 
     Choosing colors which have equal chroma and luminance provides a
     way of minimising the irradiation illusion which would otherwise
     produce a misleading impression of how large the areas are.

     The default values of chroma and luminance make it possible to
     generate a full range of hues and have a relatively pleasant
     pastel appearance.

     The RGB values produced by this function correspond to the sRGB
     color space used on most PC computer displays.  There are other
     packages which provide more general color space facilities.

     Semi-transparent colors ('0 < alpha < 1') are supported only on
     some devices: see 'rgb'.

_V_a_l_u_e:

     A vector of character strings which can be used as color
     specifications by R graphics functions.

_N_o_t_e:

     At present there is no guarantee that the colours rendered by R
     graphics devices will correspond to their sRGB description. It is
     planned to adopt sRGB as the standard R color description in
     future.

_A_u_t_h_o_r(_s):

     Ross Ihaka

_R_e_f_e_r_e_n_c_e_s:

     Ihaka, R. (2003). Colour for Presentation Graphics, Proceedings of
     the 3rd International Workshop on Distributed Statistical
     Computing (DSC 2003), March 20-22, 2003, Technische Universität
     Wien, Vienna, Austria. <URL:
     http://www.ci.tuwien.ac.at/Conferences/DSC-2003>.

_S_e_e _A_l_s_o:

     'hsv', 'rgb'.

_E_x_a_m_p_l_e_s:

     require(graphics)

     # The Foley and Van Dam PhD Data.
     csd <- matrix(c( 4,2,4,6, 4,3,1,4, 4,7,7,1,
                      0,7,3,2, 4,5,3,2, 5,4,2,2,
                      3,1,3,0, 4,4,6,7, 1,10,8,7,
                      1,5,3,2, 1,5,2,1, 4,1,4,3,
                      0,3,0,6, 2,1,5,5), nrow=4)

     csphd <- function(colors)
       barplot(csd, col = colors, ylim = c(0,30),
               names = 72:85, xlab = "Year", ylab = "Students",
               legend = c("Winter", "Spring", "Summer", "Fall"),
               main = "Computer Science PhD Graduates", las = 1)

     # The Original (Metaphorical) Colors (Ouch!)
     csphd(c("blue", "green", "yellow", "orange"))

     # A Color Tetrad (Maximal Color Differences)
     csphd(hcl(h = c(30, 120, 210, 300)))

     # Same, but lighter and less colorful
     # Turn of automatic correction to make sure
     # that we have defined real colors.
     csphd(hcl(h = c(30, 120, 210, 300),
               c = 20, l = 90, fixup = FALSE))

     # Analogous Colors
     # Good for those with red/green color confusion
     csphd(hcl(h = seq(60, 240, by = 60)))

     # Metaphorical Colors
     csphd(hcl(h = seq(210, 60, length = 4)))

     # Cool Colors
     csphd(hcl(h = seq(120, 0, length = 4) + 150))

     # Warm Colors
     csphd(hcl(h = seq(120, 0, length = 4) - 30))

     # Single Color
     hist(stats::rnorm(1000), col = hcl(240))