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WAVELET METHODS FOR
TIME SERIES ANALYSIS
Curso: ANÁLISIS DE SISTEMAS DINÁMICOS NO LINEALES:
APLICACIÓN A LOS SISTEMAS NATURALES
Prof. JOSE FCO. GOMEZ GLEZ. jfcgomez@ull.es.
1. Introduction
The first recorded mention of what we now call a ‘wavelet’ seems to
be in 1909 in a thesis by Alfred Haar.
The concept of wavelets in its present theoretical form was first
proposed by Jean Morlet and the team at the Marseille Theoretical
Physics Center working under Alex Grossmann in France.
The concept of wavelet analysis have been developed mainly by Y.
Mayer and his colleagues.
The main algorithm dates back to the work of Stephane Mallat in
1988.
Such research is particularly active in the United States, where it is
spearheaded by the work of scientists such as Ingrid Daubechies,
Ronald Coifman, and Victor Wichkerhauser.
Wavelets are a relatively new way of analyzing time series or images.
Wavelet analysis is in some cases complementary to existing
analysis techniques (e.g., correlation and spectral analysis) and in
other cases capable of solving problems for which little progress had
been made prior to the introduction of wavelets.
2. Summary of Fourier Theory
3. Why Wavelet analysis?
The results of the Fourier transform are the Fourier coefficients A(f),
which when are multiplied by a sinusoid of frequency f yield the
constituent sinusoidal components of the original signal.
To study Non-stationary Signals, in which their frequency
components are changing over time, we cannot use the Fourier
Transform because time information is lost.
To correct this deficiency, Gabor (1946) adapted the Fourier
Transform to analyze only a small section of the signal at a time.
Gabor’s adaptation, called Short-Time Fourier Transform (STFT)
maps a signal into a two-dimensional function of time and
frequency.
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