detcoef

1-D detail coefficients

Syntax

D = detcoef(C,L)

D = detcoef(C,L,N)

D = detcoef(C,L,N,'cells')

[D1,…,Dp] = detcoef(C,L,N)

Description

D = detcoef(C,L) extracts the detail coefficients at the coarsest scale from the wavelet decomposition structure [C, L]. See wavedec for more information on C and L.

D = detcoef(C,L,N) extracts the detail coefficients at the level or levels specified by N.

D = detcoef(C,L,N,'cells') returns a cell array containing the detail coefficients. A minimum of two levels must be specified. The i^th element of D contains the detail coefficients at the i^th specified level.

• If length(N)>1, the D = detcoef(C,L,N) is equivalent to D = detcoef(C,L,N,'cells').

• D = detcoef(C,L,'cells') is equivalent to D = detcoef(C,L,[1:NMAX]), where NMAX = length(L)-2.

[D1,…,Dp] = detcoef(C,L,N) extracts the detail coefficients at the levels specified by N. The length of N must equal the number of output arguments.

Examples

Detail Coefficients for 1-D Signal

This example shows how to obtain and plot the detail coefficients for an electrical current signal. This example uses zero-padding (see dwtmode).

Load the signal and select the first 3920 samples.

origmode = dwtmode('status','nodisplay');
dwtmode('zpd','nodisplay')

load leleccum; 
s = leleccum(1:3920);

Perform the decomposition at level 3 using db1. Extract the detail coefficients at levels 1, 2, and 3 from the decomposition structure.

[c,l] = wavedec(s,3,'db1');
[cd1,cd2,cd3] = detcoef(c,l,[1 2 3]);

Plot the original signal.

plot(s)
title('Original signal')
ylim([0 1000])

Plot the level 3 detail coefficients.

plot(cd3)
title('Level 3 detail coefficients (cd3)')
ylim([-60 60])

Plot the level 2 detail coefficients.

plot (cd2)
title('Level 2 detail coefficients (cd2)')
ylim([-60 60])

Plot the level 1 detail coefficients.

plot (cd1)
title('Level 1 detail coefficients (cd1)')
ylim([-60 60])

Restore the original extension mode.

dwtmode(origmode,'nodisplay')

Input Arguments

C — Wavelet decomposition vector

real-valued vector

Wavelet decomposition vector, specified as a real-valued vector. The vector C is the output of wavedec.

Data Types: single | double
Complex Number Support: Yes

L — Bookkeeping vector

vector of positive integers

Bookkeeping vector, specified as a vector of positive integers. The bookkeeping vector L contains the number of coefficients by level. The bookkeeping vector is used to parse the coefficients in the wavelet decomposition vector C. The vectors C and L are the outputs of wavedec.

Data Types: single | double

N — Detail level

positive integer | vector of positive integers

Detail level to extract from the wavelet decomposition, specified as a positive integer or a vector of positive integers.

• If N is an integer, then N must be an integer such that 1 ≤ N ≤ NMAX, where NMAX = length(L)-2.

• If N is a vector of integers, then N(j) must be an integer such that 1 ≤ N(j) ≤ NMAX, where j = 1,…,length(N).

Output Arguments

D — Detail coefficients

real-valued vector | cell array

Detail coefficients, returned as a real-valued vector or a cell array. If D is a cell array, the i^th element of D are the detail coefficients at the level specified by the i^th element of N.

D1,…,Dp — Detail coefficients

real-valued vectors

Detail coefficients, returned as set of real-valued vectors. The i^th output argument are the detail coefficients at the level specified by the corresponding element of N.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The detcoef function supports GPU array input with these usage notes and limitations:

• detcoef supports only the 'sym' and 'per' extension modes. See dwtmode.

• detcoef supports only these syntaxes:

  • D = detcoef(C,L)

  • D = detcoef(C,L,N)

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a