Documentation

Fit Tutorial:  

http://theochem.ki.ku.dk/on_line_docs/gnuplot/gnuplot_21.html

Manpage:

http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?coll=fw&db=info&fname=/usr/freeware/info_tpl/gnuplot/gnuplot_1.html  

Scripts 

--- this one does a 3D plot and a fit --- 

set terminal pdf

set style data lines

set dgrid3d 50,50,50

set view 45,135

set xlabel "Volumenstrom [m^3/h]"

set ylabel "Wasserdampfbeladung [g/kg]"

set zlabel "Trocknungsgeschwindigkeit [g/s]" 12,7

set xrange [150:240]

set yrange [30:200]

FIT_LIMIT = 1e-12

f(x,y) = a00 + (a10*x + a20*x**2) + (a01*y + a11*x*y + a21*x**2*y) + (a02*y**2 + a12*x*y**2 + a22*x**2*y**2)

fit f(x,y) 'trocknungsgeschwindigkeit_korrigiert.txt' using 1:2:3:(1) via a00,a10,a20,a01,a11,a21,a02,a12,a22

set output "trocknungsgeschwindigkeit1.pdf"

splot 'trocknungsgeschwindigkeit_korrigiert.txt' using 1:2:3 ti "Messpunkte", f(x,y) ti "Kurve der kleinsten Fehlerquadrate"