Transcription of Wavelet Transforms in Time Series Analysis
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Wavelet Transforms in Time SeriesAnalysisAndrew TangbornGlobal Modeling and Assimilation Office, Goddard Space Flight fourier What is a Wavelet ?3. Continuous and Discrete Wavelet Transforms4. Construction of Wavelets through dilation Example - Haar wavelets6. Daubechies Compactly Supported Data compression, efficient Soft Continuous transform - Morlet Wavelet10. Applications to approximating error correlationsFourier Transforms A good way to understand how wavelets work and why they are useful is bycomparing them with fourier Transforms . The fourier transform converts a time Series into the frequency domain:Continuous Transformof a function f(x): f( ) = Z f(x)e i xdxwhere f( ) represents thestrengthof the function at frequency , where Transformof a function f(x): f(k) = Z f(x)e ikxdxwherekis a discrete discrete dataf(xj),j= 1,..,N fk=NXj=1fje( i2 (k 1)(j 1)/N) The Fast fourier transform (FFT) iso(NlogN) : Single Frequency Signalf(t) = sin(2 t)012345678910 1 Coefficient Imaginary CoefficientFourier transform Discrete fourier transform (DFT) locates the single frequency and re-flection.
Fourier Transforms • A good way to understand how wavelets work and why they are useful is by comparing them with Fourier Transforms. • The Fourier Transform converts a time series into the frequency domain: Continuous Transform of a function f(x): fˆ(ω) = Z∞ −∞ f(x)e−iωxdx
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