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0.1.14 concat

Requires:

Synopsis
Concatenate several visibility data sets.

Description

The list of data sets given in the vis argument are chronologically concatenated into an output data set in concatvis, i.e. the data sets in vis are first ordered by the time of their earliest integration and then concatenated.

If there are fields whose direction agrees within the direction tolerance (parameter dirtol), the actual direction in the resulting, merged output field will be the one from the chronologically first input MS.

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.

Each appended dataset is assigned a new observation id (provided the entries in the observation table are indeed different).

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’

freqtol – Frequency shift tolerance for considering data to be in the same spwid. The number of channels must also be the same. default: ” == 1 Hz example: freqtol=’10MHz’ will not combine spwid unless they are within 10 MHz. Note: This option is useful to combine 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: ” == 1 mas (milliarcsec) example: dirtol=’1arcsec’ 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: False

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.

copypointing – Make a proper copy of the POINTING subtable (can be time consuming). If False, the result is an empty POINTING table. default: True

visweightscale – The weights of the individual MSs will be scaled in the concatenated output MS by the factors in this list. SIGMA will be scaled by 1/sqrt(factor). 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 and the SIGMA column of these MS by a factor 1/sqrt(3). default: [] (empty list) - no scaling

forcesingleephemfield – By default, concat will only merge two ephemeris fields if the first ephemeris covers the time range of the second. Otherwise, two separate fields with separate ephemerides are placed in the output MS. In order to override this behaviour and make concat merge the non-overlapping or only partially overlapping input ephemerides, the name or id of the field in question needs to be placed into the list in parameter ’forcesingleephemfield’. example: [’Neptune’] - will make sure that there is only one joint ephemeris for field Neptune in the output MS default: ” - standard treatment of all ephemeris fields



Arguments





Inputs

vis

Name of input visibility files to be concatenated

allowed:

stringArray

Default:

concatvis

Name of output visibility file

allowed:

string

Default:

freqtol

Frequency shift tolerance for considering data as the same spwid

allowed:

any

Default:

variant

dirtol

Direction shift tolerance for considering data as the same field

allowed:

any

Default:

variant

respectname

If true, fields with a different name are not merged even if their direction agrees

allowed:

bool

Default:

False

timesort

If true, sort by TIME in ascending order

allowed:

bool

Default:

False

copypointing

Copy all rows of the POINTING table.

allowed:

bool

Default:

True

visweightscale

List of the weight scaling factors to be applied to the individual MSs

allowed:

doubleArray

Default:

forcesingleephemfield

make sure that there is only one joint ephemeris for every field in this list

allowed:

any

Default:

variant

Example

 
           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=[’src2.ms’,’ngc5921.ms’], concatvis=’out.ms’, dirtol=’0.5arcsec’)  
               like the previous example but using a direction tolerance increased to  
               0.5 arcsec. Fields whose directions differ by less than this limit are  
               merged into one field with the name and direction from the  
               chronologically first input MS.  
 
           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  


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