The linear network L, on which the points will be generated,
  is determined by the argument f.
  
If f is a function, it is converted to a pixel image
  on the linear network, using any additional function arguments
  ….
If n is a single integer and f is a function or pixel image,
  then independent random points are generated on L with
  probability density proportional to f.
If n is an integer vector and f is a list of functions
  or pixel images, where n and f have the same length,
  then independent random points of several types are generated on
  L, with n[i] points of type i having probability
  density proportional to f[[i]].