Smoothbandpass: Difference between revisions

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'''Return to [[Analysis Utilities]]'''
'''Return to [[Analysis Utilities]]'''


Until casa is able to smooth the uv data prior to solving for bandpass, it may be useful to smooth the solution instead, although this is not as good as the former method. After doing this smoothing, you can use [[plotbandpass]] to overlay the smoothed solution over the original solution. ''Note that if the signal to noise of your original solution is too low, this method will introduce unphysical spikes in the output solution!'' In this case, you may have to use BPOLY option of '''{{bandpass}}'''.
If you are using casapy v3.4 or greater, then you can use the solint parameter of bandpass to smooth the uv data prior to solving for bandpass.  This will yield the best results.  If you are forced to use casapy v3.3 or earlier, then you are stuck with smoothing the solution instead, although this is not as good as the former method. After doing this smoothing, you can use [[plotbandpass]] to overlay the smoothed solution over the original solution. ''Note that if the signal to noise of your original solution is too low, this method will introduce unphysical spikes in the output solution!'' In this case, you may have to use BPOLY option of '''{{bandpass}}'''.


<source lang="python">
<source lang="python">
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<code><pre>
<code><pre>
Usage: smoothbandpass(caltable, window_len=20, window='flat', method='ri',  
Usage: smoothbandpass(caltable, window_len=20, window='flat', method='ri',  
avoidflags=True, verbose=False, fullVerbose=False, help=False, log='')
avoidflags=True, verbose=False, fullVerbose=False, help=False, log='', outputname=None)
The output table will have '_smoothXXwindow_method' appended to the name,
Unless the outputname is specified, the output table will have '_smoothXXwindow_method' appended  
where 'XX'=window_len and 'window' is the window type.  The window  
to the name, where 'XX'=window_len and 'window' is the window type.  The window  
type options are: 'flat', 'hanning', 'hamming', 'bartlett', 'blackman'.
type options are: 'flat', 'hanning', 'hamming', 'bartlett', 'blackman'.
Method types are 'ri' = real & imaginary or 'ap' = amp & phase
Method types are 'ri' = real & imaginary or 'ap' = amp & phase

Revision as of 18:11, 13 August 2012

Return to Analysis Utilities

If you are using casapy v3.4 or greater, then you can use the solint parameter of bandpass to smooth the uv data prior to solving for bandpass. This will yield the best results. If you are forced to use casapy v3.3 or earlier, then you are stuck with smoothing the solution instead, although this is not as good as the former method. After doing this smoothing, you can use plotbandpass to overlay the smoothed solution over the original solution. Note that if the signal to noise of your original solution is too low, this method will introduce unphysical spikes in the output solution! In this case, you may have to use BPOLY option of bandpass.

au.smoothbandpass(help=True)
Usage: smoothbandpass(caltable, window_len=20, window='flat', method='ri', 
avoidflags=True, verbose=False, fullVerbose=False, help=False, log='', outputname=None)
Unless the outputname is specified, the output table will have '_smoothXXwindow_method' appended 
to the name, where 'XX'=window_len and 'window' is the window type.  The window 
type options are: 'flat', 'hanning', 'hamming', 'bartlett', 'blackman'.
Method types are 'ri' = real & imaginary or 'ap' = amp & phase
avoidflags: if True (default), replace all flagged channels with the value 
            from the nearest unflagged channel prior to
            passing the data to the smoothing function. The input caltable is unchanged.
verbose: if True, print a brief summary for each antenna/spw combination with flags.
fullVerbose: if True, print each channel that is being replaced, and by which channel.
log: if not blank, then write out the verbose information to the specified log file name.

For more info, see the Wikipedia page on window functions.

Examples

CASA <3>: au.smoothbandpass('uid___A002_X3c7a84_X443.ms.split.bandpass_spw')
Avoided 201 flagged channels on pol=0, spw=0, antenna=0
Avoided 201 flagged channels on pol=1, spw=0, antenna=0

Smooth solution written to: uid___A002_X3c7a84_X443.ms.split.bandpass_spw_smooth20flat_ri