8.12.2 Color scale bars
By default, plots with color maps with single-parameter color mappings are accompanied by color scale bars, which appear by default on the right-hand side of the plot. Such scale bars may be configured using the set colorkey command. Issuing the command
by itself causes such a scale to be drawn on graphs in the default position, usually along the right-hand edge of the graphs. The converse action is achieved by:
causes Pyxplot to revert to its default behaviour, as specified in a configuration file, if present. A position for the key may optionally be specified after the set colorkey command, as in the example:
set colorkey bottom
Recognised positions are top, bottom, left and right. above is an alias for top; below is an alias for bottom and outside is an alias for right.
The format of the ticks along such scale bars may be set using the set c1format command command, which is similar in syntax to the set xformat command (see Section 8.8.8), but which uses c as its dummy variable.
The positions of the ticks along color scale bars may be set using the set c1tics command command, which has similar syntax to the set xtics command.
Example: An image of the Mandelbrot set
The Mandelbrot set is a set of points in the complex plane whose boundary forms a fractal with a Hausdorff dimension of two. A point
in the complex plane is defined to lie within the Mandelbrot set if the complex sequence of numbers
subject to the starting condition
, remains bounded.
The map of this set of points has become a widely-used image of the power of chaos theory to produce complicated structure out of simple algorithms. To produce a more pleasing image, points in the complex plane are often colored differently, depending on how many iterations
of the above series are required for
to exceed 2. This is the point of no return, beyond which it can be shown that
and that divergence is guaranteed. In numerical implementations of the above iteration, in the absence of any better way to prove that the iteration remains bounded for a certain value of
, some maximum number of iterations
is chosen, and the series is deemed to have remained bounded if
. This is implemented in Pyxplot by the built-in mathematical function fractal_mandelbrot(z,m)
, which returns an integer in the range
. set numerics complexset sample grid 500x500set size squareset nokeyset nocolkeyset log c1plot [-2:2][-2:2] fractals.mandelbrot(x+i*y,70)+1 with colormap