set terminal png
set output "./gas_prices.png"
set key on below
set xlabel "Date"
set ylabel "Cost"
set yrange[0:40]
set xdata time
set timefmt "%Y-%m-%d"
set format x "%m/%y"
plot "./gas.dat" using 1:2 with lines title "My Fill-Up Cost", "./real_gas_prices.dat" using 1:2 with lines title "National Avg. For 10 Gallons"