Level 3.1 : y = x2+(y2)/10
# 作図方法 gnuplot<<EOF clear set xrange [-20:20] set yrange [-20:20] splot x**2+(y**2)/10 set grid set contour set cntrparam levels incremental 0,20,300 set xlabel "x" set ylabel "y" set terminal png set output "func3_1.png" replot set terminal svg set output "func3_1.svg" replot set terminal pdf set output "func3_1.pdf" replot