# Description
  
  Compute and plot Allan Deviation from tab separated values files.
  
  # Usage
  
  `python allanplot.py --help`
  
  usage: allanplot.py [-h] [-f FILENAME] [-c COLUMNS [COLUMNS ...]] [-r RATE]
  
  Plot Allan Deviation from timeseries file
  
  optional arguments:
    -h, --help            show this help message and exit
    -f FILENAME           File(s) to import (default *.dat)
    -c COLUMNS [COLUMNS ...]
                          Columns to import (default 2)
    -r RATE               Time rate in seconds (default 1)
  
  Example: './allanplot.py -f 'toto.dat' -c 2 3' compute and plot Allan
  Deviation form columns 2 and 3 of toto.dat
  
  # Examples
  
  `python allanplot.py -f '**/*.dat` will load all dat files in all sub-directories of the current path.