thanks

1. Calculated Dataset
   
   You can use a script and some simple math to create a circular dataset and plot it:
   

   
   // Enter some sample values
   RADIUS=8;
   PX=18;
   PY=0;
   // Let the user edit these values
   getnum (Radius) RADIUS (X-Center) PX (Y-Center) PY (Define the Circle);
   // Calculate a circular dataset
   temp=system.math.angularunits;
   system.math.angularunits=1;
   loop(theta,1,360) {
      data1_a[theta]=PX+RADIUS*cos(theta);
      data1_b[theta]=PY+RADIUS*sin(theta);
   }
   system.math.angularunits=temp;
   // and plot it
   wo -s 0 0 0 0;
   wo -p 200 line;
   

   
   
2. Draw a Circle and Set Its Dimensions
   
   Use the Circle Tool to draw an arbitrary circle on your Graph (from above). Hold down the Alt key while double-clicking on the circle to open the Label Control dialog and find the Object Name. If the circle has no name, name it Circle. Click OK. Double-click on the circle without the Alt key to open the Shape Control dialog. Check Hollow as the Fill method and click OK. Now execute this script (assuming you've named the circle 'circle'):
   

   
   circle.dy=2*RADIUS;
   circle.dx=2*RADIUS;
   circle.y=PY;
   circle.x=PX;
   

   
   and the drawn circle should overlay the plotted data perfectly.
   
   The first method has advantages if you need to base calculations on the circular data, while the second is simpler to calculate.