Description Guy Davenport 2008-05-09 11:10:49 EDT

Support is required for weighted tree layouts in zest (and perhaps in a general form Weighted Graphs). That is where the edge length is proportional to a specified weight or distance between nodes. For example such support would allow the display for phylogenetic trees (http://en.wikipedia.org/wiki/Phylogenetic_tree). Support for right-angled connections between nodes would also be required for certain styles of phylogenetic tree. 

The first step would be to extend the GraphConnection class to a WeightedGraphConnection class that has the additional field 'weight' of type double.
 
I propose that there at least 6 (perhaps more) styles of WeightedTreeLayout. 

1) horizontal, straight connections
2) vertical, straight connections
3) horizontal, right-angle connections  
4) vertical, right-angle connections  
5) radial (see http://en.wikipedia.org/wiki/Image:MyosinUnrootedTree.jpg)
6) radial, but with a circular connections (see http://en.wikipedia.org/wiki/Image:Tree_of_life_SVG.svg)  

In the case of unrooted trees there would be many ways to draw a single tree. You would need to decide on start point for drawing (a defacto root). In calculating a layout I think that the first step would be to calculate maximum total weight from the root to a leaf node and use this to determine the scaling relative to the size of the display.