All the plots in this chapter up to now have implicitly used rectangular coordinates, usually denoted as x and y. For certain types of information, however, polar geometry is the natural coordinate system. In polar coordinates we have a radius,
r, measured from the origin, usually at the center of the graph, and an angle,
θ, usually measured counter-clockwise from the horizontal. On the gnuplot command line, the angular coordinate is called
t by default. The following is an example of a spiral illustration:
Using polar coordinates we can plot spirals and closed curves that are impossible to define explicitly using ...