I use gnuplot command below to plot trajectories
plot -22.5 lw 3,22.5 lw 3, 'hydro_15/hydro_15.01/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'black','hydro_15/hydro_15.02/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'orange','hydro_15/hydro_15.03/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'violet','hydro_15/hydro_15.04/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'red','hydro_15/hydro_15.05/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'cyan','hydro_15/hydro_15.06/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'blue','hydro_15/hydro_15.07/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'green','hydro_15/hydro_15.08/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'magenta','hydro_15/hydro_15.09/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'brown','hydro_15/hydro_15.10/tracer_com.dat' u (($2)**2+($3)**2)**0.5:4 w l lc 'coral'
Can I make it shorter maybe by using for loop or something else. Sometime I have 40 files to plot which makes command very lengthy