Implicit function plotting with gnuplot is also nice http://gnuplot-surprising.blogspot.hu/2011/09/assume-three-is-equation-fxygxy-and-we.html
Illes -- http://hal.elte.hu/fij
Implicit function plotting with gnuplot is also nice http://gnuplot-surprising.blogspot.hu/2011/09/assume-three-is-equation-fxygxy-and-we.html
Illes -- http://hal.elte.hu/fij