IDL Wavelet Toolkit User's Guide

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106 Chapter 4: IDL Wavelet Toolkit ReferenceWV_PWTThe WV_PWT function returns the partial wavelet transform of the input vector A.The transform is done using a user-inputted wavelet filter. WV_PWT is called byWV_DWT.WV_PWT is based on the routine pwt described in section 13.10 of NumericalRecipes in C: The Art of Scientific Computing, 2nd ed. (Cambridge University Press),and is used by permission.SyntaxResult = WV_PWT( A, Scaling, Wavelet, Ioff, Joff [, /DOUBLE] [, /INVERSE] )Return ValueThe result is an output vector of the same length as A, containing one stage of thepyramidal algorithm (Mallat 1989).ArgumentsAThe input vector. The length must be either less than four (4) or a power of two (2).ScalingA vector of scaling (father) coefficients, of length N.WaveletIoffJoffA vector of wavelet (mother) coefficients, of length N.An integer that specifies the support offset for Scaling. To center the scaling functionover each point in Array, set Ioff to –N/2+2.An integer that specifies the support offset for Wavelet. To center the waveletfunction over each point in Array, set Joff to –N/2+2.WV_PWTIDL Wavelet Toolkit
Chapter 4: IDL Wavelet Toolkit Reference 107KeywordsDOUBLESet this keyword to force the computation to be done in double-precision arithmetic.INVERSEIf set, the inverse transform is computed. By default, the forward transform iscomputed.Method and Result FormatThe WV_PWT function computes the wavelet coefficients for one level of thepyramidal algorithm. For a one-dimensional vector with 16 elements, one level of thepyramid appears below:Array elements[ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]\ / \ / \ / \ / \ / \ / \ / \ /s0,d0 s1,d1 s2,d2 s3,d3 s4,d4 s5,d5 s6,d6 s7,d7where Si and Di are the scaling and wavelet coefficients and i represents theposition. The wavelet coefficients are stored in Result in the following order:Result = [ s0, s1, s2, s3, s4, s5, s6, s7,d0, d1, d2, d3, d4, d5, d6, d7 ]Version History5.3 IntroducedSee AlsoWV_DWTIDL Wavelet ToolkitWV_PWT
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IDL WaveletToolkit User’sGuideIDL
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Chapter 1: Introduction to the IDL
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Chapter 1: Introduction to the IDL
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Chapter 2Using the IDL WaveletToolk
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IDL Wavelet Toolkit User's Guide

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