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Wavelet Shapes

One-dimensional analysis is based on one scaling function phi and one wavelet psi. Two-dimensional analysis (on a square or rectangular grid) is based on one scaling function and three wavelets.

The following figure shows phi and psi for each wavelet, except the Morlet wavelet and the Mexican hat, for which phi does not exist. All the functions decay quickly to zero. The Haar wavelet is the only noncontinuous function with three points of discontinuity (0, 0.5, 1). The psi functions oscillate more than associated phi functions. coif2 exhibits some angular points; db6 and sym6 are quite smooth. The Morlet and Mexican hat wavelets are symmetrical.

Figure 6-1 Various One-Dimensional Wavelets


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