tansig or logsig

Ali — Tue, 03 Nov 2009 20:22:54 -0500

hi guys,
Is it better to use 'logsig' or 'tansig' for transfer function of
output layer? is it important?

if we use tansig, can we use output data in [0 1] range (normalize)?

Re: tansig or logsig

Greg Heath — Thu, 05 Nov 2009 03:22:43 -0500

On Nov 3, 3:22 pm, Ali <vahed.k...@gmail.com> wrote:
> hi guys,
> Is it better to use 'logsig' or 'tansig' for transfer function of
> output layer? is it important?
>
> if we use tansig, can we use output data in [0 1] range (normalize)?

It depends on the output scaling.

For regression with no natural finite bounds (e.g., [0,2*pi) for
angles)
I standardize the outputs (zero mean and unit variance) and use
PURELIN.

For regression with natural finite bounds (e.g., [0,2*pi) for angles)
I normalize the outputs to [-1,1] and use TANSIG. Also used for
bipolar binary representations.

For classification the class targets are coded using columns of the
unit matrix so that outputs represent posterior probabilities
estimates.
LOGSIG is the proper choice for this scenario and , im general,
for unipolar binary inputs.

See my post on pretraining advice:

http://groups.google.com/group/comp.soft-sys.matlab/msg/0d24fcb92959575a?hl=en

Hope this helps.

Greg

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tansig or logsig

Re: tansig or logsig