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Plotting List information

Lists can also be displayed using the command PLOT. PLOT has a large number of options, some corresponding to possible list . Usually in any given list the first two columns are taken as the cartesian coordinates. This can be altered with the SET XCOLUMN and SET YCOLUMN commands.

The available plot types are:

• /1TO1 for true aspect ratio.
• /BOXES A BOXES list has four coordinate pairs associated with each element, defining the vertices of the rectangle, the object position on the slit etc. Thus a PLOT/BOXES will draw up those regions on the device. Additionally /CYCLE will draw subsequent ones in different colour pens.
• /JOIN draws arrows between corresponding pairs of (,) positions from two list slots. The user can further specify an expansion factor, by which the length of the arrow is increased, whilst the origin and direction remain the same. This option is useful to visualise the effects of transformations on an image.
• /CIRCLE draws a circle of user defined centre and radius on an existing plot.
• /ELLIPSE similarly draws an ellipse of user defined centre and dimensions on an existing plot.
• /KNOTS uses a KNOTS list to draw horizontal and vertical lines representing the spline fitting knots.
• /LINE draws in line segments to connect successive points in a list.
• /MASK plots a representation of a mask using information in the MASK list. Any coordinate of zero-weight will be be plotted as for a fiducial hole.
• /NUMBERS prints the numbers contained in a specified column of the current list, at the cartesian positions defined for each list entry.
• /SPECTRUM draws a spectrum list.
• /FIBOX for a FIBOX list.
• /FIELD draws a rectangle, taking user defined limits.
• /FIDUCIAL draws four crosses at the cardinal points a user specified distance from the origin.
• /ROH draws a representation of a row-of-holes mask. This qualifier is only for use with /MASK.
• /DIRECT for plotting of a DRCT list, in the form of an outline of the slits (and fiducial holes) and also the zero-order position.
• /LIMIT shows the limits of the field of view, as determined by CAMFIELD and COLFIELD.
• /TEXT plots up text at a user defined position

PLOT does not clear the device and so is drawn on top of any existing image or previous PLOT. For interactive displays the line colour can be changed with the command SET PEN. For hard copies plots can be made on subsequent pages by ADVANCEing the plotting window. If ADVANCE is used on an interactive display the device is simply cleared. (NB: the hardcopy file thus created must be sent to the appropriate physical device by issuing a DCL command.)