invcrossentropy_snn.m

来自「神经网络的工具箱, 神经网络的工具箱,」· M 代码 · 共 33 行

function [yl, yu] = invcrossentropy_snn(y_av, e_max)
%INVCROSSENTROPY_SNN the inverse of the crossentropy error.
%
% Syntax
%
%  [yl, yu] = invcrossentropy_snn(y_av, err)
%
% Description
%
%  INVCROSSENTROPY_SNN takes
%   y_av     - error is around y_av
%   err      - crossentropy error
%  and returns
%   yl       - lowest y for which crossentropy_snn(y, y_av) = err
%   yu       - highest y for which crossentropy_snn(y, y_av) = err
%  
% See also
%
%   CROSSENTROPY_SNN
%

% This is a rough approximation.

tmp = sqrt(2*e_max);

pp = (y_av+1)/2;
tplus = 1 - (1-pp).*exp(-tmp.^2./(1-pp)/2);
tmin = pp.*exp(-tmp.^2./pp/2);

yu = 2*tplus - 1;
yl = 2*tmin - 1;