Development/cabb-upgrade/PGFLAG

Specification

We want a simple PGPLOT-based utility to

• display UV data from a single baseline, in the format (achieved in version 1)
  • channel number on X axis
  • time on Y axis
  • amplitude or phase shown as "greyscale"
• display a cursor with 'live' readback of the amplitude/phase, channel number, frequency and timestamp
  • PGPLOT has no callback routines on cursor movement, so unable to implement live readback
  • instead have made it possible to 'measure' the point under the cursor via keypress
• it would be helpful to display the source name as well, either as a live readback, or as an annotation on the display window (perhaps at the scan boundaries)
  • not implemented in version 1.3

We want to use this to select subsets of the displayed data and apply flagging commands to the subset.

Display characteristics

• display one baseline at a time (version 1)
• we want to be able to jump to a different baseline number (forward and back thro' the sequence) (version 1)
• don't average time steps by default (make the averaging a command parameter) (version 1)
• do sum the channels such that the entire bandpass fits in the PGPLOT display window (allow turning this off via command line params)
  • PGPLOT routine PGGRAY does this automatically (version 1)
• if the uvdata array extends beyond the edges of the display window, allow scrolling (vertically or horizontally) (version 1)
• when it is possible to scroll, show an arrow (outside the display grid) pointing in the direction one can scroll. Arrow keys are the most obvious shortcut key!
  • PGPLOT uses the cursor keys in interactive mode as another way to move the mouse
  • instead version 1 uses the vi movement keys h,j,k,l for scrolling
• the cursor would ideally be an 'open plus' shape - lines extending to the edge of the display grid but with a small open area at the intersection (so you can see what is directly under the cursor).
  • unable to change PGPLOT interactive cursor shape
• zooming - allow zooming up to 1:1 display. May be useful to have higher zooms than this?
  • PGPLOT routine PGGRAY allows for easy zooming with automatic scaling (version 1)
• must support SELECT and LINE keywords (version 1)

Flagging

• when user selects a piece of data, and says 'flag it'
  • update the display to show the data flagged away (version 1)
  • allow 'undo' of the last flagging command. (version 1)
• selection:
  • by area (PGPLOT boxing) (version 1)
  • this will do single rows and columns as well.
  • however one does want to be able to flag an entire row while still zoomed in (ie data extends beyond display borders)
    • version 1 can extend the selection to the entire row/column, but only on viewed region
    • version 1.3 can extend the selection to entire row/column, past the viewed region, allowing flagging of all data while zoomed
• should be able to abort a flagging session, ie throw all flags for the current baseline and/or all baselines flagged so far.
  • version 1 can abort completely, not start again without reloading
  • version 1.3 can discard flags on displayed baseline or all baselines without restarting
• probably want to use temporary flagging files that only replace the flag file for the dataset at the end of the task
  • version 1 uses in-memory flagging, and applies only at the end
• probably want to allow logging of the flagging commands so they can be played back/edited with UVFLAG
  • version 1 logs all flags to the history, and can make BLFLAG selgen-like files, but of course the 'select' keyword cannot be used to constrain channel ranges

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