I have got a big problem with an Y-script funcion form. I'm trying to use it to specify offset (y0) (in a Lorentz fitting funcion) as a line. Can I write: "y0=a*x+b; y=y0+(2*A/PI)*(w/(4*(x-xc)^2+w^2));" and Y0 set as a dependent variable, or y0 should stay parameter?
Your script is fine. The way you have defined y0, it is just a temporary variable, and so should not be declared either as a dependent variable or as a parameter. You should declare a and b as parameters, along with A, xc, and w.