Return to Answer

Mathematica has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.
         

Mathematica has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.
         

Mathematica has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.
          GridGraph http://cs.smith.edu/~orourke/MathOverflow/GraphCenter.jpg

Mathematica has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.
         

Mathematica, in its Combinatorica Package, has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.

Mathematica has a function GraphCenter[] that computes the center of a graph (the set of vertices with minimum eccentricity--exactly your definition). You can find a description in the documentation here.
          GridGraph http://cs.smith.edu/~orourke/MathOverflow/GraphCenter.jpg