Transforming the vertex and edge attributes

The map operator is a core method for transforming distributed datasets or RDDs in Spark. Similarly, property graphs also have three map operators defined as follows:

class Graph[VD, ED] {
  def mapVertices[VD2](mapFun: (VertexId, VD) => VD2): Graph[VD2, ED]
  def mapEdges[ED2](mapFun: Edge[ED] => ED2): Graph[VD, ED2]
  def mapTriplets[ED2](mapFun: EdgeTriplet[VD, ED] => ED2): Graph[VD, ED2]
}

Each of these methods is called on a property graph with vertex attribute type VD and edge attribute type ED. Each of them also takes a user-defined mapping function mapFun that performs one of the following:

• For mapVertices, mapFun takes a pair of (VertexId, VD) as input and returns a transformed vertex attribute of type VD2.

• For mapEdges, mapFun takes an Edge object as input and returns a transformed edge attribute of type ED2.

• For mapTriplets, mapFun takes an EdgeTriplet object as input and returns a transformed edge attribute of type ED2.

Note

In each...