Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Group: Mathematical Functions
Topic: Fourier and Wavelet transforms
See also: invfwt2 fwt invfwt dwt invdwt fwtin fwtinshift

Function: fwt2
Description: The algorithm fwt2 is designed for 2 dimensional wavelet transformation. It mainly corresponds to dwt for the one dimensional case. If wished it works with the tensor product of one dimensional wavelet transforms.

Link:
Usage: c = fwt2 (x, l, h, a)
Input:
x n x n matrix, the input data, where n has to be a power of 2
l integer, l^2 is the number of the father wavelet coefficients
h m x 1 vector, wavelet basis
a integer, 0,1,2,3,... see notes
Output:
c n x n matrix, resulting coefficients

Note:

Example:
; load the wavelet library
library ("wavelet")
; initialize random generator
randomize(0)
; generate some data (line from top left to bottom right)
n = 16
i = 1:n
xo = (i.=i')
x  = xo+0.2.*normal(n,n) 
; compute bivariate wavelet coefficients
c = fwt2 (x, 4, daubechies4, 0);
; hard threshold
c = c.*(abs(c).>0.3)
; apply inverse transformation
y = invfwt2(c, 4, daubechies4, 0)
; compare orginal picture with thresholded picture
max(max(abs(y-xo),2))
Result:

Content of max
[1,]  0.48421 

Group: Mathematical Functions
Topic: Fourier and Wavelet transforms
See also: invfwt2 fwt invfwt dwt invdwt fwtin fwtinshift

Keywords - Function groups - @ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

(C) MD*TECH Method and Data Technologies, 17.8.2000