GraphRadius

GraphRadius[g] gives the minimum eccentricity of the vertices in graph g (the eccentricity of the center).

Examples

Radius of a path:

GraphRadius[PathGraph[Range[5]]]
(* 2 *)

Radius of a complete graph:

GraphRadius[CompleteGraph[10]]
(* 1 *)

Relation to diameter:

g = GridGraph[{3, 3}];
{GraphRadius[g], GraphDiameter[g]}
(* {2, 4} *)

Please visit the official Wolfram Language Reference for more details.