While trying to fit a TGraph with a “pol3”, I get (note how it “jumps”):
[code]root [18] g->Fit(“pol3”)
Minimizer is Linear
Chi2 = 2075.61
NDf = 464
p0 = 4.89194e+06 +/- 753524
p1 = -7394.77 +/- 1142.6
p2 = 3.72553 +/- 0.577519
p3 = -0.000625518 +/- 9.72989e-05
(class TFitResultPtr)141375584
root [19] g->Fit(“pol3”)
Minimizer is Linear
Chi2 = 2099.3
NDf = 464
p0 = 2.10406e+06 +/- 495473
p1 = -3167.38 +/- 751.307
p2 = 1.58883 +/- 0.379741
p3 = -0.000265534 +/- 6.3978e-05
(class TFitResultPtr)137580960
root [20] g->Fit(“pol3”)
Minimizer is Linear
Chi2 = 15384.7
NDf = 464
p0 = 4.07854e+07 +/- 5.93457e+06
p1 = -61821.9 +/- 8998.9
p2 = 31.2352 +/- 4.54841
p3 = -0.00526026 +/- 0.000766302
(class TFitResultPtr)145594664
root [21] g->Fit(“pol3”)
Minimizer is Linear
Chi2 = 2262.49
NDf = 464
p0 = 8.40135e+06 +/- 1.03222e+06
p1 = -12716.3 +/- 1565.21
p2 = 6.41525 +/- 0.791122
p3 = -0.00107867 +/- 0.000133286
(class TFitResultPtr)140055624[/code]