set term png
set title "Long trajectories"
set xlabel "x"
set ylabel "y"
unset key

r(x, y, x0, y0) = sqrt((x-x0)**2 + (y-y0)**2)
k = 1
b = 0.25
Vgauss(x, y, x0, y0) = 0.5*k*b**2 * exp(-r(x,y,x0,y0)**2 / b**2)
V(x, y) = Vgauss(x, y, 0, 0.5) + Vgauss(x, y, 0, -0.5) \
        + Vgauss(x, y, 0.5*sqrt(3), 0)

set xrange [-1.5:1.5]
set yrange [-1.5:1.5]

# set things up so we can plot a grayscale potential under our trajectories
set view map
set style data dots
set samples 200; set isosamples 200
set pm3d at b
set palette gray
set cbrange [0:0.5*k*b**2]

splot V(x, y) with pm3d nosurface, for [i=0:5] 'trajectories.data' index i using 2:3:1