How can I manually evaluate my data to validate my neural network?
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I would like to validate the data which my neural network is generating, but when I follow the steps in the doc, I receive a different answer than what is generated by my neural network.
Accepted Answer
MathWorks Support Team
on 27 Jun 2009
To replicate the calculations of a neural network, you must:
1) Pre-process the inputs.
2) Perform the calculations using the correct weights, biases, transfer functions, and connections.
3) Post-process the outputs.
The following example replicates the output of a 2 layer feed-forward backpropogation network.
inputs = [0 1 2 3 4 5 6 7 8 9 10];
% inputs = inputs + .1 *rand(size(inputs));
targets = [0 1 2 3 4 3 2 1 2 3 4];
% Create a network with 1 neuron in the first layer
net=newff(inputs,targets,1,{'tansig','tansig'},'trainlm');
% Train the network
net = init(net);
net.trainParam.epochs = 100;
[net,tr,out]=train(net,inputs,targets);
%Simulate the network with the inputs
[Y,Pf,Af,E,perf] = sim(net,inputs);
%Calculate output manually:
% Pre-process the data
for iii = 1:numel(net.inputs{1}.processFcns)
inputs = feval( net.inputs{1}.processFcns{iii}, ...
'apply', inputs, net.inputs{1}.processSettings{iii} );
end
% Calculate the network response
a1 = tansig(net.IW{1,1}*inputs + net.b{1});
Yc = tansig(net.LW{2,1}*a1 + net.b{2});
% Post-process the data
for iii = 1:numel(net.outputs{2}.processFcns)
Yc = feval( net.outputs{2}.processFcns{iii}, ...
'reverse', Yc, net.outputs{2}.processSettings{iii} );
end
close all
% View results
[Y' Yc']
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