mbostock/d3 — pull request #736 by jasondavies (2012-07-31 12:08:08+00:00)
Title: Add support for interpolating null transform lists.

For consistency with [CSS3][1], a null "from" or "to" transform list is replaced by an identity function list whose types match those of the non-null transform list.

[1]: http://www.w3.org/TR/css3-transforms/#animation