Level 2.0 : y = x

# 作図方法
gnuplot<<EOF
clear
plot x
set grid
set xlabel "x"
set ylabel "y"
set title "y = x"
set terminal png
set output "func2_0.png"
replot
set terminal svg
set output "func2_0.svg"
replot
set terminal pdf
set output "func2_0.pdf"
replot
EOF