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Equation and neural networks

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azie
azie 2013-5-29
回答： Abdelmalek Bellal 2022-1-16
i am using neural network to predict the output from 2 inputs, can matlab develop an equation based on the calculation for the predicted output?
Let say, here are my input and output
  • input >> output
  • 1 1 >> 2
  • 2 2 >> 4
and next sequence will be predicted by neural network which is
  • 3 3 >> ?
Is there any function that i can use to know the equation used by matlab to calculate next sequence (eg. output= input1 +input2)?

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采纳的回答

Greg Heath
Greg Heath 2013-5-30
HiddenVariableMatrix = tanh( InputWeightMatrix*InputVariableMatrix + Biasvector1);
OutputVariableMatrix = Biasvector2 + LayerWeightMatrix*HiddenVariableMatrix;
  2 个评论
azie
azie 2013-5-30
thanks for your response. your answer is actually a coding for ff neural network right? what i want is, the coding/function for developing the specific equation for output. which from your answer is
OutputVariableMatrix = Biasvector2 + LayerWeightMatrix*tanh( InputWeightMatrix*InputVariableMatrix + Biasvector1);
From my understanding, i need to code the above line in my programming. but is there any function that can create specifically an output equation together with assigning weight?
Greg Heath
Greg Heath 2013-5-30
All calculations are obtained via MATLAB functions which perform all of the calculations within.
See the documentation and demos in the Neural Network Toolbox.

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更多回答（2 个）

KK
KK 2016-12-10
Hi Greg
I am new to Neural Network and try to learn the theory/formula part such as formulas. Where can I find the equation you pointed out OutputVariableMatrix = Biasvector2 + LayerWeightMatrix*tanh( InputWeightMatrix*InputVariableMatrix + Biasvector1);
under Matlab Neural Netowrk Toolbox?
I try to know other formulas for non-default settings. Could you also recommend some fundamental articles for learning neural network. It is so easy to find the formula about SVM. But I googled a while and could not find a simple clear article about the output equations under neural network. Thanks!
KK
  1 个评论
Greg Heath
Greg Heath 2016-12-10
编辑：Greg Heath 2016-12-10
I don't know where MATLAB has explicitly posted that equation. Replace tanh with tansig and try searching in the NEWSGROUP and ANSWERS.
Try
IW LW TANSIG
Hope this helps.
Greg

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Abdelmalek Bellal
Abdelmalek Bellal 2022-1-16
Hello Greg,
I used a code for the exraction of wieghts and Baises but the collected vector of predictions by runing the ANN model is diffrent from what I am getting by using the mathematical equation. I believe the extracted weights are not the same weights that are use by the model or the equation is incorrcet? I tried multiple times but I am getting abnormal values that are negative and widely far from what I am getting from collceted vector of prediction with runing the model.
I added exponential to the output y because I am using Log transform.
Below is the obtained predictions from runing the model and the actual outputs: (reasonable)

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