AIPS NRAO AIPS HELP file for FINDR in 31DEC18



As of Tue Jun 19 9:55:15 2018


FINDR: Find normal and extreme amplitudes for uv data set

INPUTS

INNAME                             Input UV data
INCLASS                            Input UV data (class)
INSEQ                              Input UV data (seq. #)
INDISK                             Input UV data disk drive #
SOURCES                            Source (pointings) list
QUAL            -10.0              Source qualifier -1=>all
CALCODE                            Calibrator code '    '=>all
TIMERANG                           Time range to process.
SELBAND                            Bandwidth to select (kHz)
SELFREQ                            Frequency to select (MHz)
FREQID                             Freq. ID to select.
BIF               0.0      100.0   Lowest IF number 0=>all
EIF               0.0      100.0   Highest IF number 0=>all
BCHAN             0.0     2048.0   Lowest channel number 0=>all
ECHAN             0.0     2048.0   Highest channel number 0=>all
SUBARRAY          0.0     1000.0   Subarray, 0=>all
DOCALIB          -1.0      101.0   > 0 calibrate data & weights
                                   > 99 do NOT calibrate weights
GAINUSE                            CL/SN table to apply
DOPOL            -1.0       10.0   If >0 correct polarization.
PDVER                              PD table to apply (DOPOL>0)
BLVER                              BL table to apply.
FLAGVER                            Flag table version
DOBAND           -1.0       10.0   If >0 apply bandpass cal.
                                   Method used depends on value
                                   of DOBAND (see HELP file).
BPVER                              Bandpass table version
SMOOTH                             Smoothing function. See
                                   HELP SMOOTH for details.
UVRANGE         0.                 Min & max baseline (klambda)
SOLINT                             Time interval (sec)
SCANLENG                           Scan length (sec)
REFANT                             Reference antenna for VDIF
OPTYPE                             'VDIF', 'VRFI', 'TIME'
DOROBUST         -1.0        1.0   > 0 -> robust spectral avg
DOCAT            -1.0        1.0   > 0 => keep the XX file
DOCRT            -3.0     132.0    > 0 -> use the terminal,
                                   > 72 => terminal width
                                   0 -> no printing
                                   else use the line printer
OUTPRINT
                                   Printer disk file to save
PRTLEV                             > 0 => debug messages
BADDISK           -1.0      1000.0 Disks to avoid for scratch.
ARRAY2   @                         Answers from first source:
         @                         ARRAY2(1-5,1) robust averages
         @                         ARRAY2(6-10,1) rms of robust
         @                            averages
         @                         ARRAY2(11-20,1) fraction of
         @                            closure error by tenths.
         @                         ARRAY2(1-5,2) # > 10 sigma
         @                         ARRAY2(6-10,2) # > 20 sigma
         @                         ARRAY2(11,2) # orphans
         @                         ARRAY2(12,2) total # samples

HELP SECTION

FINDR
Type:  Task
Use:   This task computes the average weight, visibility amplitude and
       rms fluctuations in each baseline and correlator over a
       specified range of spectral channels and time.  It then
       converts the baseline-based quantities into apparent
       antenna-based quantities.  Finally, using robust averaging, it
       determines the "normal" amplitude, weight, and rms and
       deviations in these quantities.  It returns the normal values
       and some estimates of the extremes found in the selected subset
       of the data.
       The VDIF OPTYPE computes the average weight and complex
       visibility in each baseline and correlator over a specified
       range of spectral channels and time.  It then converts the
       baseline-based quantities into apparent antenna-based
       quantities.  Then it determines the amplitude of the vector
       difference between each visibility and the median of the
       visibilities in a window (in time) surrounding the visibility.
Adverbs:
  INNAME.....Input UV data file
  INCLASS....Input UV data file (class).      Standard defaults.
  INSEQ......Input UV data file (seq. #).     0 => highest.
  INDISK.....Input UV data file disk drive #. 0 => any.
  SOURCES....List of sources (pointings) to be processed.
             '*' or blank = all; a "-" before a source name means all
             except ANY source named.
  QUAL.......Only sources with a source qualifier number in the SU
             table matching QUAL will be used if QUAL is not -1.
  CALCODE...."sources" may be selected on the basis of the calibrator
             code given in the SU table.
                  '    ' => any calibrator code selected
                  '*   ' => any non blank code (cal. only)
                  '-CAL' => blank codes only (no calibrators)
             NB: The CALCODE test is applied in addition to the other
             tests, i.e. SOURCES and TIMERANG, in the selection of
             sources to process.  CALCODE affects only the selection
             of calibrators.
  TIMERANG...Time range of the data to be processed. In order: Start
             day, hour, min. sec, end day, hour, min. sec. Days
             relative to reference date.
  SELBAND....Bandwidth of data to be selected. If more than one IF is
             present SELBAND is the width of the first IF required.
             Units = kHz. For data which contain multiple
             bandwidths/frequencies the task will insist that some
             form of selection be made by frequency or bandwidth.
  SELFREQ....Frequency of data to be selected. If more than one IF is
             present SELFREQ is the frequency of the first IF
             required. Units = MHz.
  FREQID.....Frequency identifier to select (you may determine which
             is applicable from the OPTYPE='SCAN' listing produced by
             LISTR). If either SELBAND or SELFREQ are set, their
             values overide that of FREQID.  However, setting SELBAND
             and SELFREQ may result in an ambiguity.  In that case,
             the task will request that you use FREQID.
  DOCALIB....If true (>0), calibrate the data using information in the
             specified Cal (CL) table for multi-source or SN table for
             single-source data.  Also calibrate the weights unless
             DOCALIB > 99 (use this for old non-physical weights).
  BIF........First IF to select. 0=>all.
  EIF........Highest IF to select. 0=>all higher than BIF
  BCHAN......First channel to select. 0=>all.
  ECHAN......Highest channel to select.  The spectral channels are
             used as separate samples of the visibility to provide
             better statistics in determining the rms.
  SUBARRAY...Subarray number to consider. 0=>1.
  GAINUSE....CL table version number to apply.  0=> highest.
  DOPOL......If > 0.5 then correct data for instrumental polarization
             as represented in the AN or PD table.  This correction is
             only useful if PCAL has been run or feed polarization
             parameters have been otherwise obtained.  See HELP DOPOL
             for available correction modes: 1 is normal, 2 and 3 are
             for VLBI.  1-3 use a PD table if available; 6, 7, 8 are
             the same but use the AN (continuum solution) even if a PD
             table is present.
  PDVER......PD table to apply if PCAL was run with SPECTRAL true and
             0 < DOPOL < 6.  <= 0 => highest.
  BLVER......Version number of the baseline based calibration (BL)
             table to appply. <0 => apply no BL table,  0 => highest.
  FLAGVER....Specifies the version of the flagging table to be
             applied.  0 => highest numbered table.  <0 => no flagging
             to be applied.  A new FG table is created to hold the new
             flags; if FLAGVER >= 0, the FG table used on the data is
             copied into the output file before the new flags are
             computed.
  DOBAND.....If true (>0) then correct the data for the shape of the
             antenna bandpasses using the BP table specified by BPVER.
             The correction has five modes:
             (a) if DOBAND=1 all entries for an antenna in the table
             are averaged together before correcting the data.
             (b) if DOBAND=2 the entry nearest in time (including
             solution weights) is used to correct the data.
             (c) if DOBAND=3 the table entries are interpolated in
             time (using solution weights) and the data are then
             corrected.
             (d) if DOBAND=4 the entry nearest in time (ignoring
             solution weights) is used to correct the data.
             (e) if DOBAND=5 the table entries are interpolated in
             time (ignoring solution weights) and the data are then
             corrected.
  BPVER......Specifies the version of the BP table to be applied
  SMOOTH.....Specifies the type of spectral smoothing to be applied to
             a uv database . The default is not to apply any smoothing.
             The elements of SMOOTH are as follows:
             SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
               To smooth before applying bandpass calibration
                 1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
               To smooth after applying bandpass calibration
                 5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
             SMOOTH(2) = the "diameter" of the function, i.e. width
               between first nulls of Hanning triangle and sinc
               function, FWHM of Gaussian, width of Boxcar. Defaults
               (if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
               1 - 4 and 5 - 8, resp.
             SMOOTH(3) = the diameter over which the convolving
               function has value - in channels.  Defaults: 1,3,1,4
               times SMOOTH(2) used when input SMOOTH(3) < net
               SMOOTH(2).
  UVRANGE....(Minimum,Maximum) baseline (kilo-lambda) to process.
  SOLINT.....The interval over which the rms is determined.
             0 => 60 seconds.
  SCANLENG...Length of "scan" for VDIF in seconds.  The vector average
             of the visibilities over the scan is differenced from the
             individual visibility to make the "vector difference".
  REFANT.....Reference antenna suggestion for VDIF.
  OPTYPE.....Choice of methods for examining the data:
             'TIME' -> (default)
                       It computes the baseline amplitudes and rmses
                       in each SOLINT and converts them to antenna-
                       based values.  A robust method is used and
                       closure failure statistics maintained.  It then
                       saves them for later.  When all data have been
                       read, the antenna-based results are analyzed,
                       source by source, antenna by antenna.
                       Regression is used to compute the mean antenna
                       amplitude and mean rms and the rmses in these
                       parameters.  Outliers are then counted and
                       reported.  Statistics on the failure statistics
                       are also reported.
             'VDIF' -> It computes the baseline reals, imaginaries,
                       and weights in each SOLINT and converts then to
                       antenna-based values.  A robust method is used
                       and closure failure statistics maintained.  It
                       saves them for later.  When all data have been
                       read, the antenna-based results are analyzed
                       source by source, correlator by correlator.
                       First the visbility at each time is differenced
                       with the average of the visibilities
                       surrounding it.  The weights, amplitudes, and
                       amplitudes of the differences are then averaged
                       and reported.  Outliers are counted and
                       reported.  Statistics on the failure statistics
                       are also reported.
             'VRFI' -> It computes the baseline reals, imaginaries,
                       and weights in each SOLINT and saves as many as
                       it can for later.  When the source changes, the
                       buffer is full, or all data have been read, the
                       baseline-based results are analyzed correlator
                       by correlator.  First the visbility at each
                       time is differenced with the average of the
                       visibilities surrounding it.  The weights,
                       amplitudes, and amplitudes of the differences
                       are then averaged and reported.  Outliers are
                       counted and reported.
  DOROBUST...> 0 => Do robust averaging of the spectral channels in
                    each time and baseline.  Normal averaging is done
                    over time.
             <= 0 => Normal averaging (all samples included) is done
                     over all channels as well as time.
  DOCAT......> 0 => keep the XX extension file generated by the TIME
             OPTYPE.  Otherwise delete it on exit.
  DOCRT......Zero means write the flag table without comment.
             False (< 0) use the line printer if OUTPRINT = ' ' else
                   write named OUTPRINT file only.  When OUTPRINT is
                   not blank, DOCRT=-2 suppresses the page-feed
                   character on page headers and DOCRT=-3 suppresses
                   page headers and most other header information.
             True  (> 0) use the terminal interactively.  The task will
                   use the actual terminal width as a display limit
                   unless 72 < DOCRT < width.  In that case, the display
                   limit will be DOCRT characters.
  OUTPRINT...Disk file name in which to save the line printer output.
             ' ' => use scratch and print immediately for interactive
             jobs - batch jobs use OUTPRINT = 'PRTFIL:BATCHjjj.nnn'
             (jjj= job #, nnn = user #).  When OUTPRINT is not blank,
             multiple outputs are concatenated, and the file is not
             actually printed.
  PRTLEV.... Set > 0 to get various messages:
             1  Print the robust averages over time for each antenna,
                IF, and polarization and print the number of samples
                that would be self flagged and the number that would
                be flagged using the global averages.
             2. Also print the antenna-based amplitudes, rms's, and
                weights for each antenna, IF, polarization, and time.
                (You could keep the XX table and use PRTAB but this
                may be easier and neater.)
             3. Also print failure information from the routine that
                converts baseline-based data to antenna-based.
             4. Also print the antenna-based solutions from the
                solver.  This is for desperate programmers mainly.
  BADDISK....This array contains the numbers of disks on which it is
             desired that scratch files not be located.
Output adverbs:
  ARRAY2.....(We will probably rename this someday but for now we use
             this already known scratch adverb).  Using the first
             source (or the average of all sources with GAIN)
             From the robust average of robust antenna averages
             ( 1,1)  Vector-averaged amplitude or gain
             ( 2,1)  Vector-averaged data rms or amplitude of the
                     vector difference on VDIF/VRFI
             ( 3,1)  Scalar-averaged amplitude or gain
             ( 4,1)  Scalar-averaged data rms
             ( 5,1)  Weight
             ( 6,1)  RMS in Vector-averaged amplitude or gain
             ( 7,1)  RMS in Vector-averaged data rms or amplitude of
                     the vector difference on VDIF/VRFI
             ( 8,1)  RMS in Scalar-averaged amplitude or gain
             ( 9,1)  RMS in Scalar-averaged data rms
             (10,1)  RMS in Weight
             (11,1)  Fraction of data with closure failure fraction
                     > 0, < 0.1
             (12,1)  Fraction of data with closure failure fraction
                     >= 0.1, < 0.2
             ...
             (20,1)  Fraction of data with closure failure fraction
                     >= 0.9, <= 1.0
             Number of antenna time averages that differ from the
             overall average (ARRAY2(I,1)) in parameter I (I=1-5)
             by more than N times the RMS (ARRAY2(5+I,1)) in that
             parameter:
             ( 1,2)  N = 10 * RMS in Vector-averaged amplitude/gain
             ( 2,2)  N = 10 * RMS in Vector-averaged data rms/Vdif
             ( 3,2)  N = 10 * RMS in Scalar-averaged amplitude/gain
             ( 4,2)  N = 10 * RMS in Scalar-averaged data rms
             ( 5,2)  N = 10 * RMS in Weight
             ( 6,2)  N = 20 * RMS in Vector-averaged amplitude/gain
             ( 7,2)  N = 20 * RMS in Vector-averaged data rms/Vdif
             ( 8,2)  N = 20 * RMS in Scalar-averaged amplitude/gain
             ( 9,2)  N = 20 * RMS in Scalar-averaged data rms
             (10,2)  N = 20 * RMS in Weight
             (11,2)  Number of one-sample "averages" for which there
                     is no rms = number of orphans
             (12,2)  Total number of time averages * Number IFs *
                     Number polarizations
             ARRAY2(3,1), (4,1), (8,1), (9,1) (3,2), (4,2), (8,2),
             (9,2), and (11,2) are zero on VDIF and VRFI.

EXPLAIN SECTION

Explanation of the methods used


FINDR starts by averaging the calibrated and flagged data over a
period of SOLINT seconds.  Data with a time difference <= SOLINT are
included.  Thus, a SOLINT of 60 with records every 10 seconds will
include 7 records; to get only 6 set SOLINT to something > 50 and < 60
such as 55.  The data from each included antenna pair, IF, and
polarization are kept separate, but the spectral channels from BCHAN
through ECHAN are averaged together.

For OPTYPEs other than VDIF and VRFI:  During the averaging, the
apparent rms and average weight are found including all data (no
outlier rejection).  The rms and amplitude are averaged by both vector
and scalar means.

For OPTYPEs VDIF and VRFI: The averaging is done to determine the
"individual" records to be compared with the "scan" averages of such
records in a region of time centered on the individual records.
Typically, with decent signal-to-noise, one will set SOLINT for VDIF
to less than the time between records.  The "scan" averaging is done
over the scan interval using parameter SCANLENG and is done by finding
the median real and imaginary parts which should be less sensitive to
outliers.

Failures in antenna-based solutions are marked as such and regarded as
data that would be flagged by FLAGR.

===============
OPTYPE 'TIME'     The default.

The task converts the average amplitudes, rms's, and weights of the
antenna pairs into antenna-based values using the assumption that

Amp(A1,A2,I,P) = SQRT (Amp(A1,I,P) * Amp(A2,I,P))
Sig(A1,A2,I,P) = SQRT (Sig(A1,I,P) * Sig(A2,I,P))
Wt(A1,A2,I,P)  = SQRT (Wt(A1,I,P)  * Wt(A2,I,P))

It uses robust methods (outliers ignored) to compute the antenna-based
values and then counts the fraction [Fr(A,I,P)] of baselines for each
antenna that are more than 3 times the rms away from the final
solution.

The values of Amp(A,I,P), Sig(A,I,P), Wt(A,I,P) and Fr(A,I,P) are then
written to an XX table (which may be saved by setting DOCAT > 0).
When all of the data have been read and averaged and the antenna-based
results written to the XX table, these results are read back into
memory.

One source at a time, the task determines the robust average of each
of the five parameters (vector amplitude, vector rms, scalar
amplitude, scalar rms, weight) and the robust rms's in each of these
robust averages for each antenna, IF, and polarization.  By "robust"
average, we mean an average determined by repeated passes through the
data with the averaging process discarding outlier points.  The robust
average of these robust averages is then determined and printed in the
message window and returned in ARRAY2(I,1).

For each source and one antenna, IF, and polarization at a time, the
task loops over time counting the "questionable" data.  A sample is
questionable if

ABS(Par(A,I,P,t)-AvPar(A,I,P)) > N * AvParrms(A,I,P))

where Par(A,I,P,t) is the parameter value of antenna A at IF I,
polarization P, averaged at time t; AvPar(A,I,P) is the robust average
over time of that antenna, IF, and polarization, AvParrms(A,I,P) is
the uncertainty in that average over time.  Two values of N are used -
5 and 10 and the numbers of questionable samples are reported (if
PRTLEV >= 1).

The process is then repeated to compare the SOLINT-average samples in
each parameter with the global (over all antennas, IFs, polarizations)
averages.  For each source and one antenna, IF, and polarization at a
time, the task loops over time counting the "questionable" data.  A
sample is questionable if

ABS(Par(A,I,P,t)-GlobalAvPar) > N * GlobalAvParrms(A,I,P))

where Par(A,I,P,t) is the parameter value of antenna A at IF I,
polarization P, averaged at time t; GlobalAvPar is the robust average
over antenna, IF, and polarization of the robust averages over time;
and GlobalAvParrms is the uncertainty in that average over A, I, and
P.   The values of N used are 10 and 20 and the numbers of
questionable samples are reported (if PRTLEV >= 1) and are returned in
ARRAY2(1-10,2).

The task also computes the fraction of failure fractions having value
exactly 0 and 1 and in bins of width 0.1.  These are reported and the
binned values returned in ARRAY2(11,1) through ARRAY2(20,1).

===============
OPTYPE 'VDIF'

The task converts the average weights and complex visibilities of the
antenna pairs into antenna-based values using the assumption that

Amp(A1,A2,I,P) = SQRT (Amp(A1,I,P) * Amp(A2,I,P))
Phs(A1,A2,I,P) = Phs(A1,I,P) - Phs(A2,I,P)
Wt(A1,A2,I,P)  = SQRT (Wt(A1,I,P)  * Wt(A2,I,P))

It uses robust methods (outliers ignored) to compute the antenna-based
values and then counts the fraction [Fr(A,I,P)] of baselines for each
antenna that are more than 2.5 times the rms away from the final
solution.

The values of Amp(A,I,P), Phs(A,I,P) (as real and imaginary),
Wt(A,I,P), Fr(A,I,P), and reference antennas (I,P) are then written to
an XX table (which may be saved by setting DOCAT > 0).  When all of
the data have been read and averaged and the antenna-based results
written to the XX table, these results are read back into memory.  If
needed, the data are put on a consistent reference antenna basis.

One source at a time, the task then loops over each antenna, IF, and
polarization converting the time sequence of reals and imaginaries
into time sequences of amplitudes and amplitudes of the "vector
difference" between the current antenna visibility and the vector
average of antenna visibilities within SCANLENG/2 of the current
time.  Note that, in this case, the averages are generated by finding
the median value of the reals and the median value of the imaginaries.
This should be somewhat less succeptible to outliers than straight
averaging and better than robust averaging as well for the small
number of samples which will be normal.

Once source at a time, the task determines the robust averages and
rmses of the amplitudes, amplitudes of the vector differences, and the
weights over all antennas, IFs, and polarizations and reports them.
It then reports the number of samples more than 10 and 20 times this
rms from the mean for each antenna, IF, and polarization.  The
averages, rmses, and total number of deviant points are returned to
AIPS in ARRAY2 for the first source.

The task also computes the fraction of failure fractions having value
exactly 0 and 1 and in bins of width 0.1.  These are reported and the
binned values returned in ARRAY2(11,1) through ARRAY2(20,1).


===============
OPTYPE 'VRFI'

The task accumulates SOLINT averages in memory until the source
changes, the data ends, or the number of times that it can hold is
exhausted.  For each time, the task then loops over each antenna pair,
IF, and polarization finding the amplitude of the "vector difference"
between the current visibility and the vector average of visibilities
for that antenna pair within SCANLENG/2 of the current time.  Note
that, in this case, the averages are generated by finding the median
value of the reals and the median value of the imaginaries.   This
should be somewhat less succeptible to outliers than straight
averaging and better than robust averaging as well for the small
number of samples which will be normal.

The task determines the robust averages and rmses of the visibility
amplitudes, the amplitudes of the vector differences, and the weights
and reports them.  It also counts the samples that are more than 10
and 20 times the rms away from the robust averages and reports them.

The task then loops for another source or buffer load as appropriate.
The averages of the averages and rmses and the sums of the number of
deviations are returned to AIPS in ARRAY2.

AIPS