POLYGON

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POLYGON

            [GREG2\]POLYGON [(File)Name] [/VARIABLE]
            [GREG2\]POLYGON  [/PLOT]  [/FILL  [Colour]]  [/HATCH  [Ipen] [Angle]
        [Separ] [Phase]]
            [GREG2\]POLYGON [(File)Name] /RESET

        The first syntax defines the polygon either from:
        CURSOR
            If no argument and no option, the interactive cursor is  invoked  to
            define  the polygon summits. Type any key to go to next summit, C to
            correct the last one, D to delete it, and type E to end the  polygon
            definition. The last polygon side will then appear. The polygon def-
            inition may be aborted by typing Q. For graphical displays, you  may
            use  the mouse buttons for the commands. The left mouse button draws
            a vertex, the middle mouse button deletes the last vertex,  and  the
            right mouse button ends the polygon definition. After the use of the
            cursor, the polygon plot is stored in the GTV metacode in a  segment
            named POLYGON. You can delete it with the command CLEAR SEGMENT.
        FILE
            If  a  file name is given as argument, the cursor is not called. The
            summit coordinates are read from the named ASCII file (X  in  column
            1, Y in column 2).
        VARIABLE
            If  a SIC variable name is given with the /VARIABLE option, the sum-
            mit coordinates are read either from a variable array of the form:
                 VAR[NXY,2]  Real or Double
            or a structure of the form (i.e. same as output):
                 VAR%NXY         Integer or Long
                 VAR%X[VAR%NXY]  Real or Double
                 VAR%Y[VAR%NXY]  Real or Double
        Whereever they come from (cursor, file, or variable), the polygon values
        are   stored   internally;   they   can  be  printed  with  the  command
        GREG2\WRITE POLYGON, and they correspond to the variables POLY%NXY (num-
        ber of vertices), POLY%X and POLY%Y (the corresponding coordinates). The
        currently defined POLYGON is used by the commands MEAN and MASK.

        The polygon loaded by the command can be directly or later plotted  with
        the following options:
        /FILL [Colour]
            the  polygon is color-filled with the current pen colour or with the
            specified colour (see HELP PEN /COL for possibilities),
        /HATCH [Ipen] [Angle] [Separ] [Phase]
            the polygon is filled with parallel hatch lines with  the  specified
            pen (default current), with the given angle in degrees (default 45),
            separation in physical units (default 0.25 cm), and phase from 0  to
            1  to  displace  the lines by this fraction of the separation from a
            fixed reference (default 0).
        /PLOT
            the polygon contours are drawn with the current pen,
        For a color-filled and/or hatched and/or contoured polygon, these  three
        options can be combined; they will be executed in the above order.

        Finally,  the third syntax with the /RESET option allows to undefine the
        POLY% variable and free the internal buffers.