Function ROFUNC(B:real):real;
var
    N1,NM2,NMH,NML,J:integer; SUM,D,ZZ:real;
begin
    N1:=NDATAT + 1;
    NML:=N1 DIV 2;
    NMH:=N1 - NML;
    For J:=1 To NDATAT do
        ARR[J]:=YT[J] - B * XT[J];
    SORT(NDATAT, ARR);
    AA:=0.5 * (ARR[NML] + ARR[NMH]);
    Sum:=0; 
    ABDEVT:=0;
    For J:=1 To NDATAT do
    begin
        D:=YT[J] - (B * XT[J] + AA);
        ABDEVT:=ABDEVT + Abs(D);
        If D >= 0 then
            ZZ:=1
        else
            ZZ:=-1; 
        Sum:=Sum + XT[J] * ZZ;
    end; 
    ROFUNC:=Sum;
end;