#!/usr/bin/gnuplot
infile = 'longg2_50ns.dat'
set terminal postscript eps color enhanced solid font "Helvetica,20" size 14cm,7cm
set output "longg2.eps"

set border linewidth 1.5
set samples 5000

y0=1
amp=0.02
tau=1500 
x0=485

exp_decay(x) = (  x > 486 ) ? amp*exp(-(x-x0)/tau ) + y0 : 1/0  

fit [580:5000] exp_decay(x) infile u 1:6:5 via amp,tau

set ytics 0.02
set xtics 1000
set xrange [-200:5000]
set xlabel "Time (ns)"
set ylabel 'g^{2}(t)' offset 1.5,0

plot infile u ($1-x0):6:5 w yerr lw 2 lc rgb "black" t 'data', exp_decay(x+x0) t 'exp decay' lc rgb "red" lw 2

unset output
pause -1