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0.1.99 sdaverageold

Requires:

Synopsis
ASAP SD task: averaging and smoothing of spectra

Description

Task sdaverageold performs averaging in time/polarization and smoothing of the single-dish spectra. When timeaverage=True, spectra are averaged in time. Spectra within each scan ID are averaged when scanaverage=True. When polaverage=True, spectra are averaged in polarization and time (Note time averaging with polaverage=True would be discarded in future). See examples in below for details of time/polarization average. When kernel is specified (!=”), each spectrum is smoothed by convolving the kernel after averaging of spectra.

If you give multiple IFs (spectral windows) in spw, then your scantable will have multiple IFs by default. Averaging of multi-resolution (multi-IFs) spectra can be achieved by setting a sub-parameter in timeaverage, averageall = True. It handles multi-IFs by merging IFs which have overlaps in frequency coverages and assigning new IFs in the output spectra.

Set plotlevel = 1 to plot spectrum before and after smoothing, and verify=True to interactively select whether or not accept smoothing results. NOTE, so far, there is no mechanism to verify averaging of spectra in time and/or polarization.

Arguments





Inputs

infile

name of input SD dataset

allowed:

string

Default:

antenna

select an antenna name or ID, e.g. ’PM03’ (only effective for MS input)

allowed:

any

Default:

variant 0

field

select data by field IDs and names, e.g. ’3C2*’ (”=all)

allowed:

string

Default:

spw

select data by IF IDs (spectral windows), e.g. ’3,5,7’ (”=all)

allowed:

string

Default:

scan

select data by scan numbers, e.g. ’21~23’ (”=all)

allowed:

string

Default:

pol

select data by polarization IDs, e.g. ’0,1’ (”=all)

allowed:

string

Default:

timeaverage

average spectra over time [True, False] (see examples in help)

allowed:

bool

Default:

False

tweight

weighting for time averaging

allowed:

string

Default:

tintsys

scanaverage

average spectra within a scan number [True, False] (see examples in help)

allowed:

bool

Default:

False

averageall

set True only when averaging spectra with different spectral resolutions

allowed:

bool

Default:

False

polaverage

average spectra over polarizations [True, False]

allowed:

bool

Default:

False

pweight

weighting for polarization averaging

allowed:

string

Default:

tsys

kernel

type of spectral smoothing kernel (”=no smoothing)

allowed:

string

Default:

kwidth

width of smoothing kernel in channels

allowed:

int

Default:

5

chanwidth

width of regridded channels

allowed:

string

Default:

5

verify

interactively verify the results of smoothing for each spectrum. [not available for kernel=”regrid”]

allowed:

bool

Default:

False

plotlevel

plot and summarize results (0=none). See description in help

allowed:

int

Default:

0

outfile

name of output file (See a WARNING in help)

allowed:

string

Default:

outform

output file format (See a WARNING in help)

allowed:

string

Default:

ASAP

overwrite

overwrite the output file if already exists

allowed:

bool

Default:

False

Returns
void

Example

 
 
Keyword arguments:  
infile -- name of input SD dataset  
antenna -- select an antenna name or ID  
        default: 0  
        example: ’PM03’  
        NOTE this parameter is effective only for MS input  
field -- select data by field IDs and names  
        default: ’’ (use all fields)  
        example: field=’3C2*’ (all names starting with 3C2)  
                 field=’0,4,5~7’ (field IDs 0,4,5,6,7)  
                 field=’0,3C273’ (field ID 0 or field named 3C273)  
        this selection is in addition to the other selections to data  
spw -- select data by IF IDs (spectral windows)  
       NOTE this task only supports IF ID selction and ignores channel  
       selection.  
        default: ’’ (use all IFs and channels)  
        example: spw=’3,5,7’ (IF IDs 3,5,7; all channels)  
                 spw=’<2’ (IF IDs less than 2, i.e., 0,1; all channels)  
                 spw=’30~45GHz’ (IF IDs with the center frequencies in range 30-45GHz; all channels)  
        this selection is in addition to the other selections to data  
scan -- select data by scan numbers  
        default: ’’ (use all scans)  
        example: scan=’21~23’ (scan IDs 21,22,23)  
        this selection is in addition to the other selections to data  
pol -- select data by polarization IDs  
        default: ’’ (use all polarizations)  
        example: pol=’0,1’ (polarization IDs 0,1)  
        this selection is in addition to the other selections to data  
timeaverage -- average spectra over time  
        options: (bool) True, False  
        default: False  
 
    >>>timeaverage expandable parameter  
        tweight -- weighting for time averaging  
                options: ’var’   (1/var(spec) weighted)  
                         ’tsys’  (1/Tsys**2 weighted)  
                         ’tint’  (integration time weighted)  
                         ’tintsys’  (Tint/Tsys**2)  
                         ’median’  ( median averaging)  
                default: ’tintsys’  
        scanaverage -- average spectra within a scan number  
                       when True, spectra are NOT averaged over  
                       different scan numbers.  
                options: (bool) True, False  
                default: False  
        averageall -- average multi-resolution spectra  
                       spectra are averaged by referring  
                       their frequency coverage  
                 default: False  
 
polaverage -- average spectra over polarizations  
        options: (bool) True, False  
        default: False  
 
    >>>polaverage expandable parameter  
        pweight -- weighting for polarization averaging  
                options: ’var’  (1/var(spec) weighted)  
                         ’tsys’ (1/Tsys**2 weighted)  
                default: ’tsys’  
 
kernel -- type of spectral smoothing kernel  
        options: ’’, ’hanning’,’gaussian’,’boxcar’,’regrid’  
        default: ’’ (no smoothing)  
 
    >>>kernel expandable parameter  
        kwidth -- width of spectral smoothing kernel  
                options: (int) in channels  
                default: 5  
        example: 5 or 10 seem to be popular for boxcar  
                 ignored for hanning (fixed at 5 chans)  
                         (0 will turn off gaussian or boxcar)  
        chanwidth -- channel width of regridded spectra  
         default: ’5’ (in channels)  
         example: ’500MHz’, ’0.2km/s’  
        verify -- interactively verify the results of smoothing for each  
                  spectrum. When verify = True, for each input spectrum,  
                  spectra before and after the operation are displayed  
                  in a plot window. At the prompt there are four choices  
                  of action: ’Y’ (accept the operation and continue to  
                  the next input spectrum), ’N’ (reject the operation  
                  and continue to the next input spectrum), ’A’ (accept  
                  the current operation and continue non-interactively),  
                  and ’R’ (reject the current operation and exit from  
                  operation).  
                  Note that when the operation is rejected by ’N’ or ’R’,  
                  no smoothing is done to the spectrum/spectra.  
                options: (bool) True,False  
                default: False  
 
outfile -- name of output file  
        default: ’’ (<infile>_sm)  
outform -- output file format  
        options: ’ASAP’,’MS2’, ’ASCII’,’SDFITS’  
        default: ’ASAP’  
        NOTE the ASAP format is easiest for further sd  
        processing; use MS2 for CASA imaging.  
        If ASCII, then will append some stuff to  
        the outfile name  
overwrite -- overwrite the output file if already exists  
        options: (bool) True,False  
        default: False  
        NOTE this parameter is ignored when outform=’ASCII’  
plotlevel -- control for plotting and summary of smoothing results  
        options: (int) 0, 1, 2, and their negative counterparts  
default: 0 (no plotting)  
example: plotlevel=1; plot spectra before and after smoothing  
                 plotlevel=2; additionally list data before and after operation.  
                 plotlevel<0 as abs(plotlevel), e.g.  
                 -1 => hardcopy of final plot (will be named  
                 <outfile>_smspec.eps)  
 
-------------------------------------  
AVERAGING OF SPECTRA  
-------------------------------------  
Task sdaverageold has two modes of averaging spectra, i.e., time and  
polarization average.  
 
When timeaverage=True, spectra are averaged over time for each IF  
(spectral window), polarization, and beam, independently. Note that,  
by default (scanaverage=False), timeaverage=True averages spectra  
irrespective of scan IDs.  
It is possible to average spectra separately for each scan ID by setting  
a sub-parameter scanaverage=True.  
For example, the combination of parameters: scan=’0~2’, timeaverage=True, and  
scanaverage=False: averages spectra in scan ID 0 through 2 all together  
                   to a spectrum,  
scanaverage=True : averages spectra per scan ID and end up with three  
                   spectra from scan 0, 1, and 2.  
 
When polaverage=True, spectra are averaged over polarization for  
each IF (spectral window) and beam. Note that, so far, time averaging is  
automatically switched on when polaverage is set to True. This behavior  
is not desirable and will be discarded in future.  
 
-------  
WARNING  
-------  
For the GBT raw SDFITS format data as input:  
SDtasks are able to handle GBT raw SDFITS format data since the  
data filler is available. However, the functionality is not well  
tested yet, so that there may be unknown bugs.  
 


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