# AIPS HELP file for STOKES in 31DEC24

### HELP SECTION

```STOKES
Use:   Specify which Stokes parameters are to be produced or operated
upon by a process.  Legal values depend on the task.  Normally,
they include the Stokes parameters:
I       Q       U       V
the combinations of Stokes parameters:
IV      IQU     IQUV
the individual correlators:
RR      LL      RL      LR
or
VV      HH      VH      HV
and the combinations of correlators:
RRLL (RR/LL)   RLLR (RL/LR)  RLRL (RR/LL/RL/LR)
or
VVHH (VV/HH)   VHHV (VH/HV)  VHVH (VV/HH/VH/HV)
The generic words are interpreted differently depending on the
polarization present in the data:
'HALF' = RR, LL  for Stokes values > -5
= VV, HH  for Stokes values < -4
'CROS' = RL, LR  for Stokes values > -5
= VH, HV  for Stokes values < -4
'FULL' = I,  Q,  U,  V   for Stokes values > 0
RR, LL, RL, LR  for Stokes values < 0, > -5
VV, HH, VH, HV  for Stokes values < -4
In many cases, it is acceptable to substitute RR or LL for I
when the other is missing.  The code will also do this for VV
and HH which is less likely to be correct.  If you want,
"formal I" in which both RR and LL or VV and HH are required to
be present change STOKES='I' to STOKES='F'.  (The F forms of
IQU, IQUV, and IV are also accepted but they are already formal
I in the I form.)

WARNING: not all tasks will be able to understand this full
should understand this full range, but even some of these tasks
are more limited.  For example, IMAGR will image only one
Stokes value at a time: I, Q, U, or V.

Linear polarization nomenclature has been changed from X and Y to
V (vertical) and H (horizontal).  Thompson, Moran, and Swenson
define X as vertical, a definition used by the VLA in P band.
The mental tendency to make the "x" axis horizontal is the reason
for this change.  Note that some table plot tasks allow a single
character to refer to the data derived from a particular
polarization.  In these cases V refers to data from VV rather
than the Stokes V.

Null value: '    '
Null value assignment usually means 'I' or FULL

Verbs:
Procedures:
LINIMAGE......Build image cube from multi-IF data set.
VLBACRPL......Plots crosscorrelations.
VLBASNPL......Plots selected contents of SN or CL files.
ACIMG.........Makes image of autocorrelation data showing time vs
frequency
ACLIP.........Edits suto-corr data for amplitudes, phases, and weights
out of range.
ALVAR.........Plots the Allan Variance statistic of a UV data set.
ALVPR.........Prints statistics on the Allan Variance of a UV data set.
ANBPL.........Plots and prints uv data converted to antenna based
values.
APCAL.........Apply TY and GC tables to generate an SN table.
observations.
AVGWT.........Computes the average visibility weight of the included
data.
AVSPC.........Averages uv-data in the frequency domain.
BLAPP.........Applies baseline-based fringe solutions a la BLAPP.
BLING.........Find residual rate and delay on individual baselines.
BLPLT.........Plots BLCAL tables in 2 dimensions as function of
baseline and IF.
BPCOR.........Correct BP table.
BPLOT.........Plots bandpass tables in 2 dimensions as function of
time.
BPPLT.........Plots selected contents of bandpass (BP) files versus
time.
BPWGT.........Calibrates data and scales weights by bandpass
correction.
BSGRD.........Task to image beam-switched single-dish data.
CAPLT.........Plots closure amplitude and model from CC file.
CLCOR.........Applies user-selected corrections to the calibration CL
table.
CLIP..........Edits data based on amplitudes, phases, and weights out
of range.
CLOSE.........Plots closure phase or amplitude spectra averaged over
closures.
CLPLT.........Plots closure phase and model from CC file.
CLSMO.........Smooths a calibration CL table.
CPASS.........Computes polynomial spectral bandpass correction table.
CSCOR.........Applies specified corrections to CS tables.
DECOR.........Measures the decorrelation between channels and IF of uv
data.
DELZN.........Determines residual atmosphere depth at zenith and clock
errors.
DFCOR.........Applies user-selected corrections to the calibration CL
table.
DFTIM.........Makes image of DFT at arbitrary point showing time vs
frequency.
DFTPL.........Plots DFT of a UV data set at arbitrary point versus
time.
EDITR.........Interactive baseline-oriented visibility editor using the
TV.
ELFIT.........Plots/fits selected contents of SN, TY, SY, PC or CL
files.
ELINT.........Determines and removes gain dependence on elevation.
EVACL.........Evaluates statistics in closure phase and amplitude.
EVASN.........Evaluates statistics in SN/CL tables.
EVAUV.........Subtracts & divides a model into UV data, does statistics
on results.
FGCNT.........Counts samples comparing two flag tables.
FGPLT.........Plots selected contents of FG table.
FLAGR.........Edit data based on internal RMS, amplitudes, weights.
FRMAP.........Task to build a map using fringe rate spectra.
FRPLT.........Task to plot fringe rate spectra.
FTFLG.........Interactive flagging of UV data in channel-time using the
TV.
FUDGE.........Modifies UV data with user's algorithm: paraform task.
IBLED.........Interactive BaseLine based visibility EDitor.
IMAGR.........Wide-field and/or wide-frequency Cleaning / imaging task.
LISTR.........Prints contents of UV data sets and assoc. calibration
tables.
LOCIT.........Fits antenna locations from SN-table data.
LPCAL.........Determines instrumental polarization for UV data.
OMFIT.........Fits sources and, optionally, a self-cal model to uv
data.
PCPLT.........Plots pulse-cal tables in 2 dimensions as function of
time.
PDPLT.........Plots selected contents of PD tables.
PLOTC.........Plots color schems used by 3-color plot tasks.
POSSM.........Task to plot total and cross-power spectra.
QUACK.........Flags beginning or end portions of UV-data scans.
RFLAG.........Flags data set based on time and freq rms in fringe
visibilities.
RIRMS.........Computes rms of real/imag of a selected subset of a uv
data set
SDCAL.........Task to apply single dish calibration.
SDGRD.........Task to select and image random-position single-dish
data.
SDIMG.........Task to select and image random-position single-dish
data.
SHOUV.........Displays uv data in various ways.
SNBLP.........Plots selected contents of SN or CL files on a baseline
basis.
SNCOR.........Applies user-selected corrections to the calibration SN
table.
SNFIT.........Fits parabola to SN amplitudes and plots result.
SNFLG.........Writes flagging info based on the contents of SN files.
SNIFS.........Plots selected contents of SN, TY, SY, PC or CL files by
IF.
SNPLT.........Plots selected contents of SN, SY, TY, PC or CL files
versus time.
SNRMS.........Print statistics for selected contents of SN, SY, TY,
PC or CL files.
SOLCL.........Adjust gains for solar data according to nominal
sensitivity.
SPFLG.........Interactive flagging of UV data in channel-TB using the
TV.
SPLAT.........Applies calibration and splits or assemble selected
sources.
SPLIT.........Converts multi-source to single-source UV files w
calibration.
SPMOD.........Modify UV database by adding a model with spectral lines.
SPRMS.........Plots spectral statistics of a selected subset of a uv
data set.
SUFIX.........Modifies source numbers on uv data.
SYVSN.........Plots selected SY/TY data with SN solution values versus
time.
TI2HA.........Modifies times in UV data to hour angles.
TIORD.........Checks data for time baseline ordering, displays
failures.
TVFLG.........Interactive flagging of UV data using the TV.
UFLAG.........Plots and edits data using a uv-plane grid and the TV.
UV2MS.........Append single-source file to multi-source file.
UV2TB.........Converts UV autocorrelation spectra to tables.
UVCRS.........Finds the crossing points of UV-ellipses.
UVFIL.........Create, fill a uv database from user supplied
information.
UVFIT.........Fits source models to uv data.
UVFLG.........Flags UV-data.
UVFND.........Prints selected data from UV data set to search for
problems.
UVGIT.........Fits source models to uv data.
UVHGM.........Plots statistics of uv data files as histogram.
UVHIM.........Makes image of the histogram on two user-chosen axes.
UVHOL.........Prints holography data from a UV data base with
calibration.
UVIMG.........Grid UV data into an "image".
UVMAP.........Makes images from calibrated UV data.
UVMOD.........Modify UV database by adding a model incl spectral index.
UVPLT.........Plots data from a UV data base in multiple ways.
UVPRM.........Measures parameters from a UV data base.
UVPRT.........Prints data from a UV data base with calibration.
UVRMS.........Computes statistics of a selected subset of a uv data
set.
VBRFI.........Plots spectral statistics of VLBA autocorrelation data
for RFI.
VPLOT.........Plots uv data and model from CC file.
WIPER.........Plots and edits data from a UV data base using the TV.
```

AIPS