dcrossentropy_snn.m

来自「神经网络的工具箱, 神经网络的工具箱,」· M 代码 · 共 27 行

function df_da = dcrossentropy_snn(a, t)
%DCROSSENTROPY_SNN 1st derivative of CROSSENTROPY_SNN.
%
%  Syntax
%
%    df_dy = dcrossentropy_snn(y0, t0)
%
%     y0    - output
%     t0    - target
%     df_dy - derivative of CROSSENTROPY_SNN(y,t) with respect to y
%             in (y0, t0)
%
% See also
%
%   CROSSENTROPY_SNN
%

TINY = 1e-8;

a(find(a>=1.0)) = 1.0 - TINY;
a(find(a<=-1.0)) = -1.0 + TINY;

df_da = 0.5 * ( (1-t)./(1-a) - (1+t)./(1+a) );