negdist :: Functions (Neural Network Toolbox™)

negdist

Purpose

Negative distance weight function

Syntax

Z = negdist(W,P,FP)
info = negdist(code)
dim = negdist('size',S,R,FP)
dp = negdist('dp',W,P,Z,FP)
dw = negdist('dw',W,P,Z,FP)

Description

negdist is a weight function. Weight functions apply weights to an input to get weighted inputs.

negdist(W,P) takes these inputs,

W
S x R weight matrix

P
R x Q matrix of Q input (column) vectors

FP
Row cell array of function parameters (optional, ignored)

`W`	`S` x `R` weight matrix
`P`	`R` x `Q` matrix of `Q` input (column) vectors
`FP`	Row cell array of function parameters (optional, ignored)

and returns the S x Q matrix of negative vector distances.

negdist(code) returns information about this function. The following codes are defined:

'deriv'
Name of derivative function

'fullderiv'
Full derivative = 1, linear derivative = 0

'name'
Full name

'fpnames'
Returns names of function parameters

'fpdefaults'
Returns default function parameters

`'deriv'`	Name of derivative function
`'fullderiv'`	Full derivative = 1, linear derivative = 0
`'name'`	Full name
`'fpnames'`	Returns names of function parameters
`'fpdefaults'`	Returns default function parameters

negdist('size',S,R,FP) takes the layer dimension S, input dimension R, and function parameters, and returns the weight size [S x R].

negdist('dp',W,P,Z,FP) returns the derivative of Z with respect to P.

negdist('size',S,R,FP) returns the derivative of Z with respect to W.

Examples

Here you define a random weight matrix W and input vector P and calculate the corresponding weighted input Z.

W = rand(4,3);
P = rand(3,1);
Z = negdist(W,P)

Network Use

You can create a standard network that uses negdist by calling newc or newsom.

To change a network so an input weight uses negdist, set net.inputWeight{i,j}.weightFcn to 'negdist'. For a layer weight, set net.layerWeight{i,j}.weightFcn to 'negdist'.

In either case, call sim to simulate the network with negdist. See newc or newsom for simulation examples.

Algorithm

negdist returns the negative Euclidean distance:

```
z = -sqrt(sum(w-p)^2)
```