OPTIONS

  Option      Description               Default
  ------      -----------               -------

  -tick       Whether to draw major         0
              and minor ticks.
              0 = no ticks
              1 = major ticks
              2 = minor ticks
  -label      5' at start, 3' at end        0
              above arrow
  -both       5', 3' above,                 0
              and 3', 5' below arrow
  -direction  0 = ruler is plus strand      0
              -1 = ruler is minus strand

  -parallel   Whether to draw the arrow     true
              parallel to the sequence
              or perpendicular to it.

  -northeast  Force a north or east         true
              arrowhead(depending 
              on orientation)

  -east       synonym of above

  -southwest  Force a south or west         true
              arrowhead(depending 
              on orientation)

  -west       synonym of above

  -double     force-doubleheaded arrow

  -base       Draw a vertical base at the   false
              non-arrowhead side

  -scale      Reset the labels on the arrow false
              to reflect an externally 
              established scale.

Set -parallel to false to display a point-like feature such as a polymorphism, or to indicate an important location. If the feature start == end, then the glyph will draw a single arrow at the designated location:

       ^
       |

Otherwise, there will be two arrows at the start and end:

       ^              ^
       |              |

Scale: Pass in a externally established scale to reset the labels on the arrow. This is particularly useful for manually constructed images where the founding parameters of the panel are not 1-based. For example, a genetic map interval ranging from 0.1 - 0.3 can be constructed by first multiplying every value by 100. Passing

  arrow(-scale=>100);

will draw tick marks labelled appropriately to your external scale.