Wrong convolution of 2 functions

[Wile_E_Coyote]

I blame the ROOT’s “Integral” method, so try with FWHM=10 …

Convolution of two TF1

If you do not like this plot, you can also try: ROOT::Math::IntegratorOneDimOptions::SetDefaultIntegrator("Gauss"); TF1Convolution *f_conv = new TF1Convolution(f1, f1, emin, emax, false); You will then have four different curves, so you should be able to pick one for you [:mrgreen:] Well, you could try all different available ROOT’s “1-dim integrators”: “Gauss”, “GaussLegendre”, “Adaptive”, “AdaptiveSingular” and “NonAdaptive”. Seven different curves should be a “good m…

Creating TF1 from TGraph

Why are you still complaining [[-(] You now have three different integral values, so you can choose the one you like the most [:mrgreen:] Using “ROOT::Math::IntegratorOneDimOptions::SetDefaultIntegrator(…);”, you could try all different available ROOT’s “1-dim integrators”: “Gauss”, “GaussLegendre”, “Adaptive”, “AdaptiveSingular” and “NonAdaptive”. You will then have six different integral values to choose from [:mrgreen:] BTW. ROOT’s “integr…

Why is my integral zero?

I don’t think your calls to “Integral” are wrong. I guess it’s a deficiency in ROOT. It’s the “efficiency” / “efficiencyF” function which fools ROOT. It’s value “jumps” between 0 and 1 and the current “integrator” is known to misbehave in such cases. See also, for example: Simple Integral Sometimes you can try to “hide” this problem if you increase the number of points … for each of your functions try to add: SomeTF2->SetNpx(1000); SomeTF2->SetNpy(1000); But I wouldn’t really trust the res…

Integral of 2D function

A very brutal fix (works just in this case; in another cases you’ll need to “tune” the “number of points”): g2D1->SetNpx(700); g2D1->SetNpy(700); // “number of points” >= 700 I guess the problem is that your “g2dBIF1” is not smooth at the “edge” given by the “radius” (i.e. it’s not differentiable there) and the “numerical integrator” gets fooled (there’s a “jump” from about 8000 to 0). That’s not a problem for your “g2dBIF2” because the “radius” is much larger and the “jump” at the “edge” is …