Example

In the following example we define general polynomial of second degree (three parameters) and also the procedure for derivatives:

// y=b0*x*x + b1*x + b2 i.e. parabola
function SimpleParabola(const B: TVec; X: double): double;
begin
  SimpleParabola := b[0]*Sqr(x) + b[1]*x + b[2];
end;
// procedure for derivatives
procedure SimplePabolaDeriv(RegressFun: TRegressFun; X, Y: double; const Pars: TVec; const Grad: TVec);
begin
  Grad[0] := Sqr(x);
  Grad[1] := x;
  Grad[2] := 1;
end;
begin
  // ...
  MtxNonLinReg1.RegressFunction := SimpleParabola;
  MtxNonLinReg1.DeriveProcedure := SimpleParabolaDeriv;
end;