set term png set size 1.8 set grid set out 'cal.png' S = (17-1)*3600 + (51+2.8)*60 + 47 t(x) = S + x B=(24-6)*3600 E=(24+6)*3600 set title \ 'voltage at PV panel / 1 V on 3 July 2006, Kravi hora, Brno' set xlabel ' illuminance / 1 lx ' f(x) = a + b*x + c*x*x fit [0.04:1.3] f(x) '3lux.txt' using ($3 - 0.02):($2) via a,b,c plot [0:1.3] '3lux.txt' using ($3 - 0.02):($2), f(x) #rms of residuals (stdfit) = sqrt(WSSR/ndf) : 0.000663681 #variance of residuals (reduced chisquare) = WSSR/ndf : 4.40473e-07 #Final set of parameters Asymptotic Standard Error #======================= ========================== #a = -0.00147204 +/- 0.0003645 (24.76%) #b = 0.140795 +/- 0.001834 (1.303%) #c = -0.0122087 +/- 0.001496 (12.25%)