Tr[list]finds the trace of the matrix or tensor list.
Tr[list, f]finds a generalized trace, combining terms with f instead of Plus.
Tr[list, f, n]goes down to level n in list.
The trace of a matrix is the sum of the diagonal elements:
Total Diagonal Transpose Det DiagonalMatrix Eigenvalues
400+ new features, including the new Wolfram Predictive Interface, social network analysis, enterprise CDF deployment, and more »