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NRAO Home > CASA > CASA Task Reference Manual |
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0.1.127 split
Requires:
Synopsis
Create a visibility subset from an existing visibility set
Description
—————————————————————————– This is the new
implementation of split.
* The old implementation is available for a short time as oldsplit. * Task split2 has been renamed to split. The split2 alias will be removed soon. * Please, update your scripts to call split instead. —————————————————————————–
This new split task uses the MSTransform framework underneath. Split is the general purpose program to make a new data set that is a subset or averaged form of an existing data set. General selection parameters are included, and one or all of the various data columns (DATA, LAG_DATA and/or FLOAT_DATA, MODEL_DATA and/or CORRECTED_DATA) can be selected.
Split is often used after the initial calibration of the data to make a smaller Measurement Set with only the data that will be used in further flagging, imaging and/or self-calibration. Split can average over frequency (channels) and time (integrations).
Split also supports the Multi-MS (MMS) format as input. For more information about MMS, see the help of partition and mstransform.
Arguments
Inputs |
| ||
vis |
| Name of input Measurement set or Multi-MS
| |
| allowed: | string |
|
| Default: |
| |
outputvis |
| Name of output Measurement set or Multi-MS
| |
| allowed: | string |
|
| Default: |
| |
keepmms |
| If the input is a Multi-MS the output will also be a
Multi-MS. | |
| allowed: | bool |
|
| Default: | True |
|
field |
| Select field using ID(s) or name(s).
| |
| allowed: | any |
|
| Default: | variant
|
|
spw |
| Select spectral window/channels.
| |
| allowed: | any |
|
| Default: | variant
|
|
scan |
| Select data by scan numbers.
| |
| allowed: | any |
|
| Default: | variant
|
|
antenna |
| Select data based on antenna/baseline.
| |
| allowed: | any |
|
| Default: | variant
|
|
correlation |
| Correlation: ” ==> all, correlation=”XX,YY”.
| |
| allowed: | any |
|
| Default: | variant
|
|
timerange |
| Select data by time range.
| |
| allowed: | any |
|
| Default: | variant
|
|
intent |
| Select data by scan intent.
| |
| allowed: | any |
|
| Default: | variant
|
|
array |
| Select (sub)array(s) by array ID number.
| |
| allowed: | any |
|
| Default: | variant
|
|
uvrange |
| Select data by baseline length.
| |
| allowed: | any |
|
| Default: | variant
|
|
observation |
| Select by observation ID(s).
| |
| allowed: | any |
|
| Default: | variant
|
|
feed |
| Multi-feed numbers: Not yet implemented.
| |
| allowed: | any |
|
| Default: | variant
|
|
datacolumn |
| Which data column(s) to process.
| |
| allowed: | string |
|
| Default: | corrected |
|
keepflags |
| Keep *completely flagged rows* instead of dropping
them.
| |
| allowed: | bool |
|
| Default: | True |
|
width |
| Number of channels to average to form one output
channel
| |
| allowed: | any |
|
| Default: | variant 1 |
|
timebin |
| Bin width for time averaging
| |
| allowed: | string |
|
| Default: | 0s |
|
combine |
| Span the timebin across scan, state or both
| |
| allowed: | any |
|
| Default: | variant
|
|
Detailed Keyword arguments:
vis -- Name of input Measurement set or Multi-MS.
default: none;
example: vis=’ngc5921.ms’
outputvis -- Name of output Measurement set or Multi-MS (MMS).
default: none;
example: outputvis=’ngc5921_src.ms’
IMPORTANT: if a .flagversions file with the name of the output MS exist, this task will
exit with an error. The user needs to rename or remove the existing flagbackup
or choose a different output name for the MS.
keepmms -- Create a Multi-MS as the output if the input is a Multi-MS.
default: True
By default it will create a Multi-MS when the input is a Multi-MS.
The output Multi-MS will have the same partition axis of the input MMS.
See ’help partition’ for more information on the MMS format.
NOTE: It is not possible to do time average with combine=’scan’
if the input MMS was partitioned with separationaxis=’scan’
or ’auto’. In this case, the task will abort with an error.
--- Data Selection ---
field -- Select field using field id(s) or field name(s).
[run listobs to obtain the list iof d’s or names]
default: ’’=all fields If field string is a non-negative
integer, it is assumed to be a field index
otherwise, it is assumed to be a field name
field=’0~2’; field ids 0,1,2
field=’0,4,5~7’; field ids 0,4,5,6,7
field=’3C286,3C295’; fields named 3C286 and 3C295
field = ’3,4C*’; field id 3, all names starting with 4C
spw -- Select spectral window/channels
default: ’’=all spectral windows and channels
spw=’0~2,4’; spectral windows 0,1,2,4 (all channels)
spw=’<2’; spectral windows less than 2 (i.e. 0,1)
spw=’0:5~61’; spw 0, channels 5 to 61
spw=’0,10,3:3~45’; spw 0,10 all channels, spw 3 - chans 3 to 45.
spw=’0~2:2~6’; spw 0,1,2 with channels 2 through 6 in each.
spw = ’*:3~64’ channels 3 through 64 for all sp id’s
spw = ’ :3~64’ will NOT work.
NOTE: mstransform does not support multiple channel ranges per
spectral window (’;’).
scan -- Scan number range
default: ’’ = all
antenna -- Select data based on antenna/baseline
default: ’’ (all)
Non-negative integers are assumed to be antenna indices, and
anything else is taken as an antenna name.
examples:
antenna=’5&6’: baseline between antenna index 5 and index 6.
antenna=’VA05&VA06’: baseline between VLA antenna 5 and 6.
antenna=’5&6;7&8’: baselines 5-6 and 7-8
antenna=’5’: all baselines with antenna 5
antenna=’5,6,10’: all baselines including antennas 5, 6, or 10
antenna=’5,6,10&’: all baselines with *only* antennas 5, 6, or
10. (cross-correlations only. Use &&
to include autocorrelations, and &&&
to get only autocorrelations.)
antenna=’!ea03,ea12,ea17’: all baselines except those that
include EVLA antennas ea03, ea12, or
ea17.
correlation -- Correlation types or expression.
default: ’’ (all correlations)
example: correlation=’XX,YY’
timerange -- Select data based on time range:
default: ’’ (all); examples,
timerange = ’YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’
Note: if YYYY/MM/DD is missing date, timerange defaults to the
first day in the dataset
timerange=’09:14:0~09:54:0’ picks 40 min on first day
timerange=’25:00:00~27:30:00’ picks 1 hr to 3 hr 30min
on next day
timerange=’09:44:00’ data within one integration of time
timerange=’>10:24:00’ data after this time
array -- (Sub)array number range
default: ’’ = all
uvrange -- Select data within uvrange (default units meters)
default: ’’=all; example:
uvrange=’0~1000klambda’; uvrange from 0-1000 kilo-lambda
uvrange=’>4klambda’;uvranges greater than 4 kilo-lambda
uvrange=’0~1000km’; uvrange in kilometers
observation -- Select by observation ID(s)
default: ’’ = all
feed -- Selection based on the feed - NOT IMPLEMENTED YET
default: ’’ = all
datacolumn -- Which data column to use for processing (case-insensitive).
default: ’corrected’; example: datacolumn=’data’
options: ’data’, ’model’, ’corrected’, ’all’,’float_data’, ’lag_data’,
’float_data,data’, ’lag_data,data’.
NOTE: ’all’ = whichever of the above that are present. If the requested
column does not exist, the task will exit with an error.
keepflags -- Keep completely flagged rows in the output or drop them. This has no
effect on partially flagged rows. All of the channels and correlations
of a row must be flagged for it to be droppable, and a row must be
well defined to be keepable.
IMPORTANT: Regardless of this parameter, flagged data is never included in
channel averaging. On the other hand, partially flagged rows will
always be included in time averaging. The average value of the
flagged data for averages containing ONLY flagged data in the relevant
output channel will be written to the output with the corresponding
flag set to True, while only unflagged data is used on averages where
there is some unflagged data with the flag set to False.
default: True (keep completely flagged rows in the output)
--- Channel averaging parameter ---
width -- Number of input channels to average to create an output
channel. If a list is given, each bin will apply to one spw in
the selection.
default: 1 => no channel averaging.
options: (int) or [int]
example: chanbin=[2,3] => average 2 channels of 1st selected
spectral window and 3 in the second one.
--- Time averaging parameters ---
timebin -- Bin width for time averaging. When timebin is greater than 0s,
the task will average data in time. Flagged data will be included
in the average calculation, unless the parameter keepflags is set to False.
In this case only partially flagged rows will be used in the average.
default: ’0s’
combine -- Let the timebin span across scan, state or both.
State is equivalent to sub-scans. One scan may have several
state ids. For ALMA MSs, the sub-scans are limited to about
30s duration each. In these cases, the task will automatically
add state to the combine parameter. To see the number of states
in an MS, use the msmd tool. See help msmd.
NOTE: It is not possible to do time average with combine=’scan’
if the input MMS was partitioned with separationaxis=’scan’
or ’auto’. In this case, the task will abort with an error.
default: ’’ (separate time bins by both of the above)
options: ’scan’, ’state’, ’state,scan’
examples:
combine = ’scan’; can be useful when the scan number
goes up with each integration as in many WSRT MSs.
combine = [’scan’, ’state’]: disregard scan and state
numbers when time averaging.
combine = ’state,scan’; same as above.
More information about CASA may be found at the
CASA web page
Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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