Issue with Sigmoidnet function input

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Sharmila Biswas
Sharmila Biswas on 7 Sep 2019
Answered: Roshni Garnayak on 11 Sep 2019
Can someone please post what sigmoidnet function, under nonlinear ARX model in the system identification toolbox, is taking as input and how it is taking a time series data?
More precisely, the function of the sigmoidnet is written below,
F(x) = (x-r)*P*L + a_1 f((x-r)*Q*b_1+c_1) + .. ... + a_n f((x-r)*Q*b_n+c_n) + d
where f is the sigmoid function and n is the number of units of the function.
But, in the above formulation, what is x? and how the regressor mean (r) is calculated?

Answers (1)

Roshni Garnayak
Roshni Garnayak on 11 Sep 2019
x is an m-dimensional row vector representing the regressors and r is the mean of the regressors x. To understand the structure of nonlinear ARX models, refer to pages 11-18 to 11-19 of the following documentation:
Refer to pages 11-63 to 11-64 of the above documentation for an example that preforms a low-level computation of the nonlinearity response for the “sigmoidnet” network function.

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