Step by step calculation neural network output

Hi all!

I don't understand what are the different steps for the calculation of a NN output. I tried to do a step-by-step calculation, but i think i missed something: I tried: output = MyTransferFunc( synaptics * input + biases ); But the result is different of output = myneuralnetwork(input);

My question is: why ??

Thanks all !

Answer 1

[Greg Heath]

It depends on what type of network and default properties you used.

The first expression does not include

 1. a hidden layer 
 2. input and target normalization
 3. output un-normalization

Search Answers for my code using the keyword

tsettings

Hope this helps.

Thank you for formally accepting my answer

Greg

Answer 2

[AlfredLeMark]

Thank you for your answer. After checking, there is one hidden layer in my neural network, but i considered that in my calcul. About your second and third point, how can I check if my neural netword normalizes the inputs? (same question with the outputs ^^)

[Greg Heath]

All net properties can be obtained via

net = net % NO SEMICOLON

[AlfredLeMark]

Thank you very much! In the properties, I found something: in the Mynet.inputs, there is a nnnetInput, and in this object there is a table called "range". The Help explains: "This property defines the minimum and maximum values of the input data used to configure the input, or zero if the input is unconfigured."

In my case, the range seems like a Nx2 matrix (N = size of an input) with some values (first column = lowest values, and second column largest values) .

The File Help doesn't specifically explain how the inputs are configured. Do you know how please ?

Thank you for your help.

[Greg Heath]

Look and see that MAPMINMAX is a default property. Use help and doc to see what limits that yields.

Also see what happens when MAPMINMAX is replaced by MAPST and ''.

On the other hand, the output data limits may be affected by the output transfer function. For example, if you keep the MAPMINMAX default for the output but specify logsig for the output transfer function, there is a obvious incompatibility. Not sure how that is resolved.

HTH

Greg