Suppose I have a graph which is like this:
A--B--C--D
What is the diameter and radius of this graph?
Here r = 1 and d = 3 and r < d/2 ..right ?
Suppose I have a graph which is like this:
A--B--C--D
What is the diameter and radius of this graph?
Here r = 1 and d = 3 and r < d/2 ..right ?
The diameter is $3$, but the radius is $2$: the eccentricities of $A,B,C$, and $D$ are $3,2,2$, and $3$, respectively, and the radius is the minimum of the eccentricities.
Note that you can never have r