reset

set title ""
set xlabel "[Linsenabstand in cm]"
set ylabel "[1/f in 1/cm]"
set grid xtics ytics

f(x) = m * x + a

fit f(x) 'DatenAbbe4.txt' us ($1):(1/$3):(abs(-1/$3**2)*$4) via m,a

plot \
'DatenAbbe4.txt' us 1:(1/$3):2:(abs(-1/$3**2)*$4) notitle lt 1 w xyerrorbars, \
f(x) notitle lt 1 \

set output "abbe4.eps"
set term postscript enhanced eps color; replot