Check out the new GeoGebra Google app. It has the exact functionality which the pattern editor should have:
GeoGebra is dynamic mathematics software for education in secondary schools that joins geometry, algebra, and calculus. On the one hand, GeoGebra is a dynamic geometry system. You can do constructions with points, vectors, segments, lines, conic sections as well as functions and change them dynamically afterwards. On the other hand, equations and coordinates can be entered directly. Thus, GeoGebra has the ability to deal with variables for numbers, vectors and points, finds derivatives and integrals of functions, and offers commands like Root or Extremum. It is a free and open source software.
[via Susan Spencer]