set terminal png
set xlabel "t"
set ylabel "x,y"
set nokey # これを含めると，凡例が表示されない．
set style line 1 lt 1 lw 5 pt 3 ps 1.0 # lw 5 は線の太さ．
plot [0:200][-3:5] "results.dat" using 1:2 with lines linestyle 1,\
"results.dat" using 1:3 with points,\
"results.dat" using 1:4 with points