set grid
set title "Focal length as a function of distance from center"
set xlabel "x/R"
show xlabel
set ylabel "f/R"
show ylabel
plot "sphere-focus-1.N_1.1.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_1.15.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_1.2.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_1.3.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_1.4.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_1.5.txt" with lines linewidth 1.5 lc 7, \
"sphere-focus-1.N_1.7.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_2.0.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_3.0.txt" with lines linewidth 1.5, \
"sphere-focus-1.N_5.0.txt" with lines linewidth 1.5