reset

set encoding iso_8859_1
set title "1/a über R"
set xlabel "[R in {/Symbol W}]"
set ylabel "[1/a in 1/m]"
set grid xtics ytics
set key top left

f(x) = a*x + b
fit f(x) 'Daten21a.txt' us ($1):(1/($2)) via a,b

plot 'Daten21a.txt' us ($1):(1/($2)) title 'Messwerte' lt 1, \
     f(x) title 'Ausgleichsgerade' lt 3

set output "21a.eps"
set term postscript enhanced eps color; replot