function h = por(p, prpor, pori, cpor, varargin)
n = numel(varargin);
if n == 0
    h = pori .* (1 + cpor .* (p - prpor));
else
    prporf = varargin{1};
    cporf = varargin{2};
    rpt = varargin{3};
    hm = pori .* (1 + cpor .* (p - prpor));
    hf = pori .* (1 + cporf .* (p - prporf));
    h = rpt .* hm + ~rpt .* hf; 
end