# What are those functions?

https://root.cern/doc/master/langaus_8C.html

What are names of math formulas, that are used in order to achive a chart looking like that?
I tried to find some chi squared algorithms, but none of them is usable in order to fit the curve like in the image. The code alone doesn’t tell me anything, it’s unreadable and unusable for me.

Hi @bambo34 ,
and welcome to the ROOT forum! The tutorial description mentions that is a convolution of a Gaussian and a Landau distribution, can you be more specific as to what names of what formulas you need?

Cheers,
Enrico

Maybe in another way, because i don’t know which thing should i look for, could someone replace this data in the example from the link, compile it, and send me how the diagram looks like? I can’t install this thing on windows, i already lost my nerves.

Int_t data[35] = {6, 3, 0, 1, 1, 1, 0, 5, 3, 4, 0, 3, 3, 1, 0, 2, 1, 0, 2, 1, 4, 4, 2, 3, 2, 1, 2, 1, 3, 1, 2, 2, 2, 2, 2};

//replace this:
Int_t data[100] = {0,0,0,0,0,0,2,6,11,18,18,55,90,141,255,323,454,563,681,
737,821,796,832,720,637,558,519,460,357,291,279,241,212,
153,164,139,106,95,91,76,80,80,59,58,51,30,49,23,35,28,23,
22,27,27,24,20,16,17,14,20,12,12,13,10,17,7,6,12,6,12,4,
9,9,10,3,4,5,2,4,1,5,5,1,7,1,6,3,3,3,4,5,4,4,2,2,7,2,4};

TH1F *hSNR = new TH1F("snr","Signal-to-noise",400,0,400);

for (Int_t i=0; i<100; i++) hSNR->Fill(i,data[i]);     //<--- 35 instead of 100