- The `FEATURE` Command:
  - Creates a new plot feature and adds it to a plot.
  - As you can with layers, you can specify your own feature by creating a class and passing the name to the `FEATURE` command.
  - Some of the feature types and flags are:
    SYMBOL - Some of the symbols included in NeXtMidas are:

          CROSS   - A 'x' symbol.       TRIANGLE,  TRI  - A triangle symbol.
          PLUS    - A '+' symbol.       UTRIANGLE, UTRI - A triangle (up).
          STAR    - A '*' symbol.       DTRIANGLE, DTRI - A triangle (down).
          CIRCLE  - A circle symbol.    RTRIANGLE, RTRI - A triangle (right).
          SQUARE  - A square symbol.    LTRIANGLE, LTRI - A triangle (left).
          DIAMOND - A diamond Symbol.   ASCII-<str>     - An ASCII string <str>.
          DOT     - A small dot/pixel.  <single letter> - A single ASCII letter.
          ARROW   - A block arrow.      NULL            - No symbol used.
          AERO    - An airplane symbol.

    DATA - Highlights the enclosed data. Typically used on a line plot to highlight a portion of interest.
    HLINE - Draws horizontal lines at X-DX/2 and X+DX/2.
    VLINE - Draws vertical lines at Y-DY/2 and Y+DY/2.
    BOX - Draws a box centered at (X,Y) with height DY and width DX.
    CIRCLE - Draws a circle centered at (X,Y) with radius of MAX(DY,DX).
    OVAL - Draws an oval centered at (X,Y) with height DY and width DX.
    ELPS - Draws a geodetic ellipse centered at (X,Y) with height DY and width DX. The ellipse will follow the curvature of the Earth.
    LTAG,RTAG,TTAG,BTAG - Labels the feature with a tag along the left/right/top/bottom axis. The tags are drawn outside of the axis unless IPLT is specified.
    IPLT - Shows the tags (see LTAG,RTAG,TTAG,BTAG) inside the plot axis.
    VRIDE - The vertical position of the feature (Y) should ride along the plot value. Typically used in combination with SYMBOL on a line plot to mark the data value at a given X value.
    LABEL - Show a label for the feature.
    INVERSE - When coloring the feature use the inverse color of the plot data. Typically used over a raster plot to ensure that the feature will stand out regardless of the color of the plot.
    FILLED - Fills a BOX, CIRCLE, or OVAL feature. Note that this has no affect on symbols, which have a separate SYMBOLFILL option (see above).
  - In some cases, types/flags can be combined as a `|` separated list. For example,

        nM> plot/bg/id=myplot apenny
        nM> feature label=flines plot=myplot table={NAME="FLINES",TYPE=HLINE|VLINE,X=20,Y=20,COLOR=BLUE}

  puts a horizontal and vertical line below the word Liberty on the raster.
  - See EXPLAIN FEATURE for a complete list of features and symbol types.
  - As with nearly ALL NeXtMidas commands, the FEATURE command has a test macro, `test_feature.mm` which you can use as a reference.