f(z):=(z-1)/(z+2);
fx(r,t):=''(realpart(f(r*(cos(t)+%i*sin(t))))); /*関数の実部*/
fy(r,t):=''(imagpart(f(r*(cos(t)+%i*sin(t)))));  /* 同虚部 */
p:[];         /* 同じ窓に重ね描きするため描画指令をリストにする */
for r: 0.1 thru 1.0 step 0.1 do
  (p:append(p,
   [[parametric,fx(r,t),fy(r,t),[t,0,2*%pi],
               /* [gnuplot_preamble,"set term size 500,800"], */
     [gnuplot_preamble,"set size ratio -1"],
     [gnuplot_preamble,"unset key"],
     [color,black],
     [box,false]
    ]
   ]
   )
  );
for a: 0.0 thru 2*%pi step %pi/10 do
  (p:append(p,
   [[parametric,fx(t,a),fy(t,a),[t,0,1.0],
               /* [gnuplot_preamble,"set term size 500,800"], */
     [gnuplot_preamble,"set size ratio -1"],
     [gnuplot_preamble, "unset key"],
     [color,black],
     [box,false]
    ]
   ]
   )
  ); /*パラメータrはエラーになる*/
plot2d(p);                  /* gnuplot の描画指令を呼び出す */
