WWZ Transform Code for Python

This is a Python code for timeseries analysis using WWZ transformations. It uses Foster’s abbreviated Morlet Wavelet to analyse timeseries using a WWZ (Weighted Wavelet-Z) transform. (Foster, G., 1996, http://adsabs.harvard.edu/full/1996AJ....112.1709F)

The algoritm is mostly translated from Templeton’s Fortran code (Templeton, M., 2004, http://adsabs.harvard.edu/full/2004JAVSO..32...41T).

Details of the mathematics, coding and fundamental time series analysis (especially in astronomy) is available in my thesis (Turkish): http://eayd.in/msc

Citing This Code

You can cite this code with its DOI and citing my thesis:

Aydin, M. E., 2017. eaydin/WWZ: v1.0.0, Zenodo, http://doi.org/10.5281/zenodo.375648

Aydin, M. E., 2014, Dynamic Power Spectra On The Basis Of Wavelet Transform, M.S. Thesis, Ankara University

Usage

It can either be used as a module import in another Python script or used as a standalone program. It supports paralellization, yet only in standalone mode.

Dependencies: Python 2.6+ (not Python 3 ready) and NumPy

There is also a Lomb-Scargle script in the repo for ease of use and comparison.

usage: wwz.py [-h] -f FILE -o OUTPUT -l FREQ_LOW -hi FREQ_HIGH -d FREQ_STEP -c
          DCON [-g] [-m] [-t TIME_DIVISIONS] [--time] [--no-headers]
          [-p PARALLEL]
Input arguments can be read from a file. The file descriptor
    prefix is '@'.
In order to read argument from a file named args.txt,
    the argument @args.txt should be passed.
An example for args.txt:
    -f=myinputfile.txt
    -o=theoutputfile.output
    -m
    --freq-step=0.001
    -l=0.001
    -hi=0.01
    -c=0.001
    -p=0
You can pass arguments from file and commandline at the same time.
If two same arguments passed by this method, the latter will be
used. So if you want to override some arguments in a an argument
file, specify the file first.
An example usage for our earlier @args.txt is as:
    python wwz.py @args.txt -c=0.0125
The above command will use the settings in args.txt but will
use c=0.0125 instead of c=0.001
Comments and blank lines are NOT allowed in argument files.
Import this script via Python to use it as a module, rather than
a standalone script. (import wwz)
optional arguments:
  -h, --help            show this help message and exit
  -f FILE, --file FILE  the Input File, Raw Lightcurve
  -o OUTPUT, --output OUTPUT
                        the Output File Name
  -l FREQ_LOW, --freq-low FREQ_LOW
                        the Low Frequency Value
  -hi FREQ_HIGH, --freq-high FREQ_HIGH
                        the High Frequency Value
  -d FREQ_STEP, --freq-step FREQ_STEP
                        the dF value, incremental step for Frequency
  -c DCON, --dcon DCON  the C constant for the Window Function
  -g, --gnuplot-compatible
                        the Output file is GNUPlot compatible, which means the
                        tau's will be grouped so that pm3d can easily map.
                        Default value is 'False'.
  -m, --max-periods     Creates a secondary output with the maximum Periods
                        for each single tau. This can be drawn in 2D. The
                        output filename is derived from the -o option, added
                        'max_periods'. Default value is 'False'.
  -t TIME_DIVISIONS, --time-divisions TIME_DIVISIONS
                        The Time Divisions value. Templeton assumes this as
                        50. VStars from AAVSO leaves this optional contrary to
                        Templeton, yet it's default value is also 50.
  --time                Calculate the time of operation in seconds and print
                        to standard output.
  --no-headers          Doesn't print headers to output files if set. Default
                        is 'False'.
  -p PARALLEL, --parallel PARALLEL
                        Created threads to speed up the process. Default value
                        is '1', which means single thread. '0' means number of
                        detected CPUs, can be overridden.

Example Outputs

Below is an example of the X-Ray source (observed by the RXTE Satellite) with data, Lomb-Scargle and WWZ output.

Example Graph

The example below shows the main advantage of WWZ over LS. There is periodicity that LS failed to detect, with a period of about 166 days. Also note the change in frequency.

Sco X-1

The SMCX-1 graph below shows how peak frequency detected by LS can be misleading, since that frequency value actually changes (very low at 51500 and 54500 MJD) and the alias of the detected LS peak (at around 29 days period) is not detected by the WWZ algorithm (which is a good thing).

SMCX-1