How to set the encoder transfer function in autoencoder
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I want to set the encoder transfer function by myself. But I do not how to do it. Can the encoder transfer function be changed by myself
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SANA
le 16 Nov 2018
First you make an autoencoder and generate its function, the code for generating the function of autoencoder is:
autoenc = trainAutoencoder(Data, 300,...
'MaxEpochs', 100,...
'L2WeightRegularization', 0.001,...
'SparsityRegularization', 4,...
'SparsityProportion', 0.05,...
'ScaleData', true);
generateFunction(autoenc)
The generated function open in MATLAB editor with the name of neural_function, I renamed it my_autoencoder and the transfer function is mentioned there, so you can edit it as you wish, code is below:
function [y1] = my_encoder(x1)
%NEURAL_FUNCTION neural network simulation function.
%
% Generated by Neural Network Toolbox function genFunction, 15-Nov-2018 15:50:26.
%
% [y1] = neural_function(x1) takes these arguments:
% x = 5088xQ matrix, input #1
% and returns:
% y = 5088xQ matrix, output #1
% where Q is the number of samples.
%#ok<*RPMT0>
% ===== NEURAL NETWORK CONSTANTS =====
% Input 1
x1_step1.xoffset = [-10;-11;-11;-12;-1]
x1_step1.gain = [0.090;0.9090;0.9090;0.90909;0.0769]
x1_step1.ymin = 0;
% Layer 1
b1 = [-0.115;0.768;0.7066;0.5009303396;0.1249019302]
IW1_1 = [-0.0947 0.7320 0.3146 0.494636173 -0.0951171]
b2 = [3.5409901027442902688;3.6635759144424437928]
LW2_1 = [-1.1707436273955371675 1.5786236406994880177 -1]
% Output 1
y1_step1.ymin = 0;
y1_step1.gain = [0.0909090909090909;0.07]
y1_step1.xoffset = [-10;-11;-11;-12;-12]
% ===== SIMULATION ========
% Dimensions
Q = size(x1,2); % samples
% Input 1
xp1 = mapminmax_apply(x1,x1_step1);
% Layer 1
a1 = logsig_apply(repmat(b1,1,Q) + IW1_1*xp1);
% Layer 2
a2 = logsig_apply(repmat(b2,1,Q) + LW2_1*a1);
% Output 1
y1 = mapminmax_reverse(a2,y1_step1);
end
% ===== MODULE FUNCTIONS ========
% Map Minimum and Maximum Input Processing Function
function y = mapminmax_apply(x,settings)
y = bsxfun(@minus,x,settings.xoffset);
y = bsxfun(@times,y,settings.gain);
y = bsxfun(@plus,y,settings.ymin);
end
% **********************************************
% ************ Enhance encoder here ************
% Sigmoid Positive Transfer Function
function a = logsig_apply(n,~)
a = 1 ./ (1 + exp(-n));
end
% ************ Enhance encoder here ************
% **********************************************
% Map Minimum and Maximum Output Reverse-Processing Function
function x = mapminmax_reverse(y,settings)
x = bsxfun(@minus,y,settings.ymin);
x = bsxfun(@rdivide,x,settings.gain);
x = bsxfun(@plus,x,settings.xoffset);
end
You can change decoder function as well. Enjoy !!!
Frédéric BERTHOMMIER
le 28 Sep 2023
Modifié(e) : Frédéric BERTHOMMIER
le 28 Sep 2023
I changed the decoder transfer function to recover a PCA equivalent which I checked::
autoenc = trainAutoencoder(Data,4,'MaxEpochs',5000,'DecoderTransferFunction','purelin');
This substitutes to the generation of a .m function as proposed before for obtaining a PCA equivalent. Note that the encoder transfer function cannot be modified.
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