Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
The matlab wavelet toolbox documentation and examples do not describe how to form wavelet spectra from a time series. The way I do spectra using the wavelet toolbox is as follows: 1. I call cwt.m to get the wavelet coefficients. 2. I then form a new matrix of abs(coefs)^2 to get the wavelet energy density at a given location in wavelet space. 3. I use the morlet wavelet, so i can find the frequency = 1./scale. Where scale is returned by cwt.m. 4. If a contour plot is made of the wavelet energy density, where the x axis is time and the y axis is frequency, the plot indicates wavelet energy density as a function of freq and time. 5. If I take a vertical cut through the plot in part 4, and plot wavelet energy density (y axis) versus frequency (x axis) does this represent a local spectra? Is the above procedure esentially correct? Does anyone have any IDL code to check these results? Any suggestions greatly appreciated. Thanks! Rick McDaniel