reset

set xrange [90:260]
set yrange [0:0.0055]

set title "Diagramm zur Aufgabe 1.4a"
set xlabel "[Anodenspannung {U} in V]"
set ylabel "[Kreisradius^2 in m^2]"
set grid xtics ytics

f(x) = m * x + a
g(x) = c * x + d

fit f(x) 'Datenem1.txt' us ($1):($2) via m,a
fit g(x) 'Datenem1.txt' us ($1):($3) via c,d

plot \
'Datenem1.txt' us ($1):($2) title "I = 1 A" lt 1, \
f(x) title "Ausgleichsgerade g1 (I = 1 A)" lt 1, \
'Datenem1.txt' us ($1):($3) title "I = 2 A" lt 3, \
g(x) title "Ausgleichsgerade g2 (I = 2A)" lt 3

set output "em1.eps"
set term postscript enhanced eps color; replot