set title "Gaussian Low-pass Filter profiles"
set xlabel "Frequency units"
set xtics ("0.0" 0, "0.1" 50, "0.2" 100, "0.3" 150, "0.4" 200, "0.5" 250)

plot 'dgflt005.dat' using 1:3 title "radius 0.05" with lines, \
'dgflt010.dat' using 1:3 title "radius 0.10" with lines, \
'dgflt025.dat' using 1:3 title "radius 0.25" with lines