    link.vertex(index)

Return the vertex at `index`.

    link.vertex(index, vertex [, opt])

Update the vertex at `index` with value of `vertex`. By default the new value is merged into the old value. Pass the `{ rewrite: true }` option along to disregard the old value.

A vertex has only two properties, `x` and `y`. It may be defined as a g.Point object.

Example vertex:

    link.vertex(0, {
        x: 100,
        y: 200
    });

Note that all vertices are stored in an array on the link model under the attribute `vertices`. Use the `link.vertices` function to access the array.