Neural Network Toolbox™

Log-sigmoid transfer function

Graph and Symbol

Syntax

• A = logsig(N,FP)
  dA_dN = logsig('dn',N,A,FP)
  info = logsig(code)
  

Description

logsig is a transfer function. Transfer functions calculate a layer's output from its net input.

logsig(N,FP) takes N and optional function parameters,

N	S x Q matrix of net input (column) vectors
FP	Struct of function parameters (ignored)

and returns A, the S x Q matrix of N's elements squashed into [0, 1].

logsig('dn',N,A,FP) returns the S x Q derivative of A with respect to N. If A or FP is not supplied or is set to [], FP reverts to the default parameters, and A is calculated from N.

logsig('name') returns the name of this function.

logsig('output',FP) returns the [min max] output range.

logsig('active',FP) returns the [min max] active input range.

logsig('fullderiv') returns 1 or 0, depending on whether dA_dN is S x S x Q or S x Q.

logsig('fpnames') returns the names of the function parameters.

logsig('fpdefaults') returns the default function parameters.

Examples

Here is the code to create a plot of the logsig transfer function.

• n = -5:0.1:5;
  a = logsig(n);
  plot(n,a)
  

Assign this transfer function to layer i of a network.

• net.layers{i}.transferFcn = 'logsig';
  

Algorithm

logsig(n) = 1 / (1 + exp(-n))

See Also

sim, tansig

Provide feedback about this page

linkdist

mae

© 1984-2008- The MathWorks, Inc.    -   Site Help   -   Patents   -   Trademarks   -   Privacy Policy   -   Preventing Piracy   -   RSS