# 出力設定
set terminal pdfcairo size 4in,3in font "Arial,12"
set output 'path_length_plot.pdf'

set xlabel "generation"
set ylabel "path length"
set grid

set xrange [0:100]
set yrange [0:80]

set xtics 10
set ytics 10

# データのプロット
# $0 は行番号（0から開始）を意味します
# 1列目:min, 2列目:avg, 3列目:max を想定
plot 'output.dat' using 0:1 with lines title "Min", \
     ''         using 0:2 with lines title "Avg", \
     ''         using 0:3 with lines title "Max"