entrupd

Entropy update (wavelet packet)

Syntax

Tupd = entrupd(T,ent,par)

Description

entrupd is a one- and two-dimensional wavelet packet utility.

Tupd = entrupd(T,ent,par) returns, for a wavelet packet tree T, the updated tree Tupd using the entropy function ent with the optional parameter par.

example

Examples

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Change Wavelet Packet Tree Entropy

Open Live Script

Load a signal. Save the current extension mode, then set the mode to zero padding.

load noisdopp
x = noisdopp;
origMode = dwtmode("status","nodisp");
dwtmode("zpd","nodisp")

Use the wpdec function to decompose the signal x at level 2 with the Haar wavelet using Shannon entropy.

t = wpdec(x,2,"haar","shannon");

Read the entropy from all nodes.

nodes = allnodes(t);
ent = read(t,"ent",nodes);
ent'

ans = 1×7
10⁴ ×

   -5.8615   -6.8204   -0.0350   -7.7901   -0.0497   -0.0205   -0.0138

Update the nodes entropy to "threshold".

t = entrupd(t,"threshold",0.5);
nent = read(t,"ent");
nent'

ans = 1×7

   937   488   320   241   175   170   163

Restore the extension mode to the original setting.

dwtmode(origMode,"nodisp")

Input Arguments

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`T` — Tree
`dtree` object | `ntree` object | `wptree` object

Tree, specified as a dtree, ntree, or wptree object.

`ent` — Entropy function
`"shannon"` | `"log energy"` | `"threshold"` | `"sure"` | `"norm"` | `"user"` | `"FunName"`

Entropy function, specified as one of the following:

Entropy Function (`T`)	Threshold Parameter (`par`)	Comments
`"shannon"`		`par` is not used.
`"log energy"`		`par` is not used.
`"threshold"`	`0 ≤ par`	`par` is the threshold.
`"sure"`	`0 ≤ par`	`par` is the threshold.
`"norm"`	`1 ≤ par`	`par` is the power.
`"user"`	String	`par` contains the file name of your own entropy function, with a single input `x`.
"FunName"	No constraints on `par`	FunName is any string other than the previous entropy functions listed. FunName contains the file name of your own entropy function, with `x` as input and `par` as an additional parameter to your entropy function.

ent and the threshold parameter par together define the entropy criterion. For more information, see wpdec.

Note

The "user" option is historical and kept for compatibility, but it is obsoleted by the last option described in the table above. The FunName option does the same as the "user" option and in addition gives the possibility to pass a parameter to your own entropy function.

`par` — Threshold parameter
real number | string

Threshold parameter, specified by a real number or a string. par and the entropy function ent together define the entropy criterion.

Version History

Introduced before R2006a