ROOT Version: 6.18/04 Platform: Linux Hi all! I have plotted efficiency curves, and now I want to fit sigmoid functions to them. I tried to fit a sigmoid function to the first efficiency curve (the red one), which is called eff[0]. [c1] I tried: TF1 *sigm = new TF1("sigm", "(1/(1+ TMath::Exp(-…

Try (before fitting): sigm->SetParameters(0.5, 50.); In ROOT, before you try to fit your graph or histogram, you MUST set “reasonable” initial values for ALL parameters of your function (except for some “built-in” formulas, like “gaus”, for which the standard fit procedure can automatically “guess”…

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Sigmoid fit to efficiency plot

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Wile_E_Coyote March 23, 2020, 12:02pm 10

Fit function uses initial parameter values Newbie

ROOT Version: 6.18/04 Platform: Linux I defined a sigmoid function with 2 parameters (and set the initial parameter values). I am now trying to fit this function to a plot (called fun[1]), however my ‘fit’ always just takes my initial parameter values, even though that is definitely not the best fit. Most of the time I also get the message saying that STATUS = FAILED, a few times, however, I got STATUS = CONVERGED, but that result clearly wasn’t the best fit. I tried: TF1 *sigm = new TF1("si…

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