set polar unset polar show polar
There have been changes made to polar mode in version 3.7, so that scripts for gnuplot versions 3.5 and earlier will require modification. The main change is that the dummy variable t is used for the angle so that the x and y ranges can be controlled independently. Other changes are: 1) tics are no longer put along the zero axes automatically -- use set xtics axis nomirror; set ytics axis nomirror; 2) the grid, if selected, is not automatically polar -- use set grid polar; 3) the grid is not labelled with angles -- use set label as necessary.
In polar coordinates, the dummy variable (t) is an angle. The default range of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see set angles (p. )).
The command unset polar changes the meaning of the plot back to the default rectangular coordinate system.
The set polar command is not supported for splots. See the set mapping (p. ) command for similar functionality for splot (p. )s.
While in polar coordinates the meaning of an expression in t is really r = f(t), where t is an angle of rotation. The trange controls the domain (the angle) of the function, and the x and y ranges control the range of the graph in the x and y directions. Each of these ranges, as well as the rrange, may be autoscaled or set explicitly. See set xrange (p. ) for details of all the ranges (p. ) commands.
set polar plot t*sin(t) plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)
The first plot uses the default polar angular domain of 0 to 2*pi. The radius and the size of the graph are scaled automatically. The second plot expands the domain, and restricts the size of the graph to [-3:3] in both directions.
You may want to set size square to have gnuplot try to make the aspect ratio equal to unity, so that circles look circular. See also
http://www.gnuplot.info/demo/polar.htmlpolar demos (polar.dem)
http://www.gnuplot.info/demo/poldat.htmlpolar data plot (poldat.dem).