Level 2.2 : z = x2+y2
# 作図方法 gnuplot<<EOF clear splot x**2 + y**2 set grid set xlabel "x" set ylabel "y" set title "z = x**2 + y**2" set terminal png set output "func2_2.png" replot set terminal svg set output "func2_2.svg" replot set terminal pdf set output "func2_2.pdf" replot EOF