RooChebychev parameters inside function

[KisooLee]

Hello

I would like to reproduce chebychev polinomials in the plain root.
To do this I would like to understand how is the parameter works inside RooChebychev function.

If I define a function like following
RooChebychev* bkgch = new RooChebychev(“bkgch”, “Chebychev background”, *(ws->var(“mass”)), RooArgList(p0, p1));
, there are two parameters p0, p1.

And the definition of second order chevychev polinomial is
T2(x) = 2x^2 -1

Then, how the parameters are applied to this function?

T2(x) = 2(x-p0)^2 - 1 + p1?
or some different shape?

Thank you

[StephanH]

Hello @KisooLee,

it computes the sum of the polynomials, i.e.

Sum_i a_i * T_i

but I guess that the constant a_0 * T_0 is suppressed.