def graphFromMatFile(matFileName):
"""
Generate a sparse graph from a Matlab file of ego and alters and their transmissions. This is a mostly
disconnected graph made up of pairs of connected vertices, i.e each vertex has degree 1.
"""
examplesList = ExamplesList.readFromMatFile(matFileName)
numExamples = examplesList.getNumExamples()
numFeatures = examplesList.getDataFieldSize("X", 1)
numVertexFeatures = numFeatures/2+1
vList = VertexList(numExamples*2, int(numVertexFeatures))
sGraph = SparseGraph(vList)
for i in range(0, examplesList.getNumExamples()):
v1Index = i*2
v2Index = i*2+1
example = examplesList.getSubDataField("X", numpy.array([i])).ravel()
vertex1 = numpy.r_[example[0:numFeatures/2], numpy.array([1])]
vertex2 = numpy.r_[example[numFeatures/2:numFeatures], numpy.array([0])]
sGraph.setVertex(v1Index, vertex1)
sGraph.setVertex(v2Index, vertex2)
sGraph.addEdge(v1Index, v2Index)
return sGraph
