stockwelltransform / README.rst

Code from the NIH core imaging group MEG c code python module

requirements for compilation: fftw3 libraries a C compiler (tested with gcc so far) numpy (tested with 1.3)

  • note: I am working on getting this to work on windows at some point but it does not work currently -clm 11/2010

see also Code from Dr. Stockwell's web site for the stockwell transform[user]=viewCategory&fatcat_id=2&module_title=pagemaster

Stockwell, R.G, L mansinha, and R. P. Lowe. Localization of the complex spectrum: The S-Transform. IEEE Transactions on Signal Processing, 44(4) pp998--1001, 1996.


from pylab import *

# The way the basic module works is, for a signal x y = # will return its complex valued transform # the amplitude "spectra" can be obtained with

ampy = abs(y)

# The rows in the interval [0,n/2) label the number of cycles during # the entire period of x (ie, it uses the length L of x as the longest # time)

# So, to covert this back to hz # Let # Fs=<sampling interval in Hz>

# Let Tn = float(L * Fs) # total time, say in seconds, of x

# row ii -> ii/L # Then the freq of row ii is freq[ii] = ii/Tn