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Marker Offset

If the Auto Offset box is checked, the marker's offset from the vertex will be computed automatically. (The primary marker will be placed with its origin coinciding with the vertex, but the secondary marker will be offset from the primary marker according to whether any duplicate markers have been specified and according to the line width.) If this box is not checked, the marker will be offset according to the length specified in the adjoining box. Examples: in Figure 9.9(a) both the start and end markers have been set to the LaTeX style marker with an offset of -10, and in Figure 9.9(b) both the start and end markers are composite markers formed from a bar primary marker and a pointed secondary marker, where the secondary marker's offset has been set to 2bp. Note that setting the secondary marker's offset to 0 is equivalent to using the overlay function.

Note that markers are placed along the gradient vector, so the marker may not necessarily lie on the path. For example, in Figure 9.10, a marker with offset 10bp has been placed at the end of a Bézier curve. The marker's offset has moved it along the gradient vector, away from the curve.

   
 markeroffset1 markeroffset2  
 (a) (b)  
Figure 9.9: Disabling the marker auto offset: (a) a negative offset makes the marker protrude off the end of the line; (b) the secondary marker has an offset of 2bp so that it is only slightly behind the primary marker.

bezieroffset
Figure 9.10: Changing a marker's offset moves it along the gradient vector.


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