The specified number n of random points is
generated with uniform distribution on the network L.
The random points are generated using runifpointOnLines.
If n is an integer vector, then a multitype point pattern is
generated, with n[i] random points of type i.
If ex is given, then it serves as an example for determining
n and L. The default value of n
will be the number of points in ex
(or the number of points of each type in ex if it is
multitype).
The default value of L will be
the network on which ex is defined.