18.5. Polymarker.   

Instead of drawing lines through a set of points, we may wish just to mark the points. 


 Mark the points, construct a polynomial to fit the points if possible

via some fit technique and then generate a line from the polynomial.


    
Polymarker plots

   
                Fig. 18.2 : Polymarker plots



 Use different polyline representations to give different curve fitting

approximations.

Polymarker(N,X,Y)
where the arguments are as for polyline: Polyline (N,X,Y) Polymarker (N,X,Y)
will plot the points and mark them as well. The symbol placed at the point is central and the first 5 marker types are 

             1            .

             2            +

             3            *     Note all of these will be centred.

             4            O

             5            X

The polymarker index can be set :
set polymarker index (N)
to get different markers.

A marker types can be associated with an index via
set polymarker representation(WS,PMI,MT,MS,PMCI) WS = workstation PMI = Polymarker Index MT = marker type defined as above. MS = marker scale factor = as for LW in polyline. PMCI = Polymarker Colour Index.

How do we implement polymarker? 


 Could use symbol to position draw '.', '+', 'X', 'O', etc.

Or could use plot to position and then do relative draws to

produce + * O.

First would be easiest but would cause problems in size and

possibly colour attribute realization.

Therefore use plot type implementation.

How GKS do we make our implementation? That is, how do we check that it conforms to the standard? What are legitimate deviations?

GKS exists at a number of implementation levels, i.e. supporting output, input, segments, etc. Each of these levels are defined and allow a gradual implementation to develop.