function d=dnulltf(n,a)
%DNULLTF Null transfer derivative function.
%
%  Syntax
%
%    dA_dN = dnulltf(N,A)
%
%  Warning!!
%
%    This function may be altered or removed in future
%    releases of the Neural Network Toolbox. We recommend
%    you do not write code which calls this function.

% Mark Beale, 11-31-97
% Copyright 1992-2002 The MathWorks, Inc.
% $Revision: 1.8 $

d = zeros(size(a));