When plotting functions in polar mode, the rrange may be autoscaled. When plotting data files in polar mode, the trange may also be autoscaled. Note that if the trange is contained within one quadrant, autoscaling will produce a polar plot of only that single quadrant.
Explicitly setting one or two ranges but not others may lead to unexpected results. See also
http://www.gnuplot.info/demo/poldat.htmlpolar demos.