Object:

** 31 ** **Date of origin:** China ~ 300BC, Germany 1693

**Author/inventor/context:** Unknown, Leibniz; basic to most scientiﬁc ﬁelds

A matrix is a table of numbers or mathematical expressions arranged in rows and columns. Manipulations, of adjacency matrices, are basic to graph theory (as used in social networks), of sparse matrices to data mining, and of stochastic matrices to PageRank. Amenable to direct or iterative computation, their ﬁnite elements describe a manipulable world. Relationships and their transformations expressed in matrix mathematics drive computer graphics, weather prediction and futures trading. The ﬁrst form of quantum mechanics (Heisenberg) used matrices to describe combinations of states. While matrix manipulation is now a grey middle layer, it can kill since drone warfare is driven by a disposition matrix.

## Dan Mcquillan