set size 1.0, 1.0
#set terminal postscript color portrait enhanced dashed lw 1 "Helvetica" 28
set terminal jpeg  enhanced large font arial size 800,600

set output "fig4.jpg"
#set title '=6*40 nm'


set xlabel 's [mm]'          
set ylabel 'n^2'
set yr [8000:13000]
set xr [2.0:4.0]

f(x)=a*x
fit f(x) 'ns.dat' using  ($1):($2*$2) via a


plot "ns.dat"  using ($1):($2*$2) ps 4 notitle, f(x) title 'n^2=a*s'