dwt

Builtin index · Signal processing

result = dwt(x)

Input: x · Output: result

What it is

x is a length-N real vector (N should be even).

Overloads

One call shape — this function is not overloaded.

Code	Input	Output	Description
`result = dwt(x)`	`x` vectornot documented yet	`result` matrix	Returns a `(2, N/2)` matrix — row 0 is the approximation band, row 1 is the detail band (Qu has no multi-return). One level of the orthogonal Haar discrete wavelet transform; only the Haar family is implemented.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

  D = dwt(x)
  approx = D[0, :]
  detail = D[1, :]
  xr = idwt(D)                 # reconstructs x exactly

from numerics-dsp

How it works

One level of the (orthogonal) Haar discrete wavelet transform. No single-vector return in this value model, so the two output bands come back as the rows of a (2,N/2) matrix: row 0 is the approximation, row 1 is the detail. Only the Haar family is implemented today (documented, not silently approximated).

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.