Concat

Help on concat task:

Concatenate several visibility data sets.

The list of data sets given in the vis argument are concatenated into an output data set in concatvis. If concatvis already exists (e.g., it is the same as the first input data set), then the other input data sets will be appended to the concatvis data set. 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.

Keyword arguments: vis -- Name of input visibility files to be combined

       default: none; example: vis = 'mydata.ms',
            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: 
          concat(vis=['src2.ms','ngc5921.ms'], concatvis='src2.ms')
              will concatenate 'ngc5921.ms' into 'src2.ms', and the original
              src2.ms is lost

          concat(vis=['src2.ms','ngc5921.ms'], concatvis='out.ms') 
              will concatenate 'ngc5921.ms' and 'src2.ms' into a file named 
              'out.ms'; the original 'ngc5921.ms' and 'src2.ms' are untouched.

          concat(vis=['v1.ms','v2.ms'], concatvis = 'vall.ms')
             then
          concat(vis=['v3.ms','v4.ms'], concatvis = 'vall.ms')
            vall.ms will contains v1.ms+v2.ms+v3.ms+v4.ms

    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.

timesort -- If true, the output visibility table will be sorted in time.

       default: false.  Data in order as read in.
       example: timesort=true
    Note: There is no constraint on data that is simultaneously observed for
       more than one field; for example multi-source correlation of VLBA data.