virtualconcat Namespace Reference

Functions
def	virtualconcat

---

Function Documentation

def virtualconcat.virtualconcat	(		vis = [''],
			concatvis = '',
			freqtol = '',
			dirtol = '',
			respectname = True,
			visweightscale = [],
			keepcopy = False,
			copypointing = True
	)

Concatenate several visibility data sets into a multi-MS

The list of data sets given in the vis argument are moved into an output
multi-MS data set concatvis and virtually concatenated. 

NOTE: This task will modify the input datasets by moving them and reindexing them.
If you want to keep a copy of your original data, please set the parameter 
keepcopy to True.

There is no limit to the number of input data sets.

If none of the input data sets have any scratch columns (model and corrected
columns), none are created in the concatvis.  Otherwise these columns are
created on output and initialized to their default value (1 in model column,
data in corrected column) for those data with no input columns.

Spectral windows for each data set with the same chanelization, and within a
specified frequency tolerance of another data set will be combined into one
spectral window.

A field position in one data set that is within a specified direction tolerance
of another field position in any other data set will be combined into one
field.  The field names need not be the same---only their position is used.

Each appended dataset is assigned a new observation id if the corresponding
rows in the observation table are not the same.

Keyword arguments:
vis -- Name of input visibility files to be combined
default: none; example: vis = ['src2.ms','ngc5921.ms','ngc315.ms']
concatvis -- Name of visibility file that will contain the concatenated data
note: if this file exits on disk then the input files are 
      added to this file.  Otherwise the new file contains  
      the concatenated data.  Be careful here when concatenating to
      an existing file.
default: none; example: concatvis='src2.ms'
         example: concatvis='outvis.ms'

other examples: 
   virtualconcat(vis=['src2.ms','ngc5921.ms'], concatvis='out.mms') 
       will concatenate 'ngc5921.ms' and 'src2.ms' into a file named 
       'out.mms'; the original 'ngc5921.ms' and 'src2.ms' are gone.
       'out.mms' is a multims. As most of the data is only moved, not 
       copied, this is faster and subsequent tasks can run in parallel
       on the subMSs of out.mms.
   virtualconcat(vis=['src2.ms','ngc5921.ms'], concatvis='out.mms', keepcopy=True) 
       will concatenate 'ngc5921.ms' and 'src2.ms' into a file named 
       'out.mms'; the original 'ngc5921.ms' and 'src2.ms' are as before
       but you consume more disk space and time for the copy.
       .

     Note: run flagmanager to save flags in the concatvis

freqtol -- Frequency shift tolerance for considering data to be in the same
   spwid.  The number of channels must also be the same.
default: ''  do not combine unless frequencies are equal
example: freqtol='10MHz' will not combine spwid unless they are
   within 10 MHz.
Note: This option is useful to conbine spectral windows with very slight
   frequency differences caused by Doppler tracking, for example.

dirtol -- Direction shift tolerance for considering data as the same field
default: '' means always combine.
example: dirtol='1.arcsec' will not combine data for a field unless
   their phase center differ by less than 1 arcsec.  If the field names
   are different in the input data sets, the name in the output data
   set will be the first relevant data set in the list.

respectname -- If true, fields with a different name are not merged even if their 
direction agrees (within dirtol). 
default: True

visweightscale -- The weights of the individual MSs will be scaled in the concatenated
output MS by the factors in this list. Useful for handling heterogeneous arrays.
Use plotms to inspect the "Wt" column as a reference for determining the scaling 
factors. See the cookbook for more details.
example: [1.,3.,3.] - scale the weights of the second and third MS by a factor 3.
default: [] (empty list) - no scaling

keepcopy -- If true, a copy of the input MSs is kept in their original place.
default: false

copypointing -- If true, the POINTING table information will be present in the output.
        If false, the result is an empty POINTING table.
 default: true

Definition at line 13 of file virtualconcat.py.

References vla_uvfits_line_sf.verify, and task_virtualconcat.virtualconcat().