 along with hue and chroma, using a simple linear
function (fitted by least squares).
<code>hclplot</code> shows a chroma-luminance plane, keeping hue at a fixed
level (by default displayed in the main title of the plot). If the hue
is, in fact, not approximately constant, the hue varies along with
chroma and luminance, using a simple linear function (fitted by least
squares.
</p>
</li>
<li><p> Diverging with two (approximately) constant hues: This case is
visualized with two back-to-back sequential display