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NRAO Home > CASA > CASA Cookbook and User Reference Manual |
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3.3.2.15 Example session using plotxy
The following is an example of interactive plotting and flagging using plotxy on the Jupiter 6cm continuum VLA dataset. This is extracted from the script jupiter6cm_usecase.py available in the script area.
This assumes that the MS jupiter6cm.usecase.ms is on disk with flagautocorr already run.
vis = ’jupiter6cm.usecase.ms’
# The fields we are interested in: 1331+305,JUPITER,0137+331
selectdata = True
# First we do the primary calibrator
field = ’1331+305’
# Plot only the RR and LL for now
correlation = ’RR LL’
# Plot amplitude vs. uvdist
xaxis = ’uvdist’
yaxis = ’amp’
multicolor = ’both’
# The easiest thing is to iterate over antennas
iteration = ’antenna’
plotxy()
# You’ll see lots of low points as you step through RR LL RL LR
# A basic clip at 0.75 for RR LL and 0.055 for RL LR will work
# If you want to do this interactively, set
iteration = ’’
plotxy()
# You can also use flagdata2 to do this non-interactively
# (see below)
# Now look at the cross-polar products
correlation = ’RL LR’
plotxy()
#---------------------------------------------------------------------
# Now do calibrater 0137+331
field = ’0137+331’
correlation = ’RR LL’
xaxis = ’uvdist’
spw = ’’
iteration = ’’
antenna = ’’
plotxy()
# You’ll see a bunch of bad data along the bottom near zero amp
# Draw a box around some of it and use Locate
# Looks like much of it is Antenna 9 (ID=8) in spw=1
xaxis = ’time’
spw = ’1’
correlation = ’’
# Note that the strings like antenna=’9’ first try to match the
# NAME which we see in listobs was the number ’9’ for ID=8.
# So be careful here (why naming antennas as numbers is bad).
antenna = ’9’
plotxy()
# YES! the last 4 scans are bad. Box ’em and flag.
# Go back and clean up
xaxis = ’uvdist’
spw = ’’
antenna = ’’
correlation = ’RR LL’
plotxy()
# Box up the bad low points (basically a clip below 0.52) and flag
# Note that RL,LR are too weak to clip on.
#---------------------------------------------------------------------
# Finally, do JUPITER
field = ’JUPITER’
correlation = ’’
iteration = ’’
xaxis = ’time’
plotxy()
# Here you will see that the final scan at 22:00:00 UT is bad
# Draw a box around it and flag it!
# Now look at whats left
correlation = ’RR LL’
xaxis = ’uvdist’
spw = ’1’
antenna = ’’
iteration = ’antenna’
plotxy()
# As you step through, you will see that Antenna 9 (ID=8) is often
# bad in this spw. If you box and do Locate (or remember from
# 0137+331) its probably a bad time.
# The easiset way to kill it:
antenna = ’9’
iteration = ’’
xaxis = ’time’
correlation = ’’
plotxy()
# Draw a box around all points in the last bad scans and flag ’em!
# Now clean up the rest
xaxis = ’uvdist’
correlation = ’RR LL’
antenna = ’’
spw = ’’
# You will be drawing many tiny boxes, so remember you can
# use the ESC key to get rid of the most recent box if you
# make a mistake.
plotxy()
# Note that the end result is we’ve flagged lots of points
# in RR and LL. We will rely upon imager to ignore the
# RL LR for points with RR LL flagged!
More information about CASA may be found at the
CASA web page
Copyright © 2010 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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