[kernel] improve gnuplot file
#set term X11
-resultfile = 'resultNETS.ref'
+resultfile_ref = 'resultNETS.ref'
resultfile = 'resultNETS-WITHPROJ.ref'
resultfile = 'result.dat'
plot \
resultfile every ::2 u 1:2 t "Ball position" w l,\
resultfile every ::2 u 1:3 t "Ball Velocity" w l,\
-resultfile every ::2 u 1:4 t "Reaction force" w l
+resultfile every ::2 u 1:4 t "Reaction force" w l,\
+resultfile_ref every ::2 u 1:2 t "Ball position" w l,\
+resultfile_ref every ::2 u 1:3 t "Ball Velocity" w l,\
+resultfile_ref every ::2 u 1:4 t "Reaction force" w l
