// specific cum value cutoff.
func (g *Graph) DiscardLowFrequencyNodes(nodeCutoff int64) NodeSet {
	return makeNodeSet(g.Nodes, nodeCutoff)
}

// DiscardLowFrequencyNodePtrs returns a NodePtrSet of nodes at or over a
// specific cum value cutoff.
func (g *Graph) DiscardLowFrequencyNodePtrs(nodeCutoff int64) NodePtrSet {
	cutNodes := getNodesAboveCumCutoff(g.Nodes, nodeCutoff)
	kept := make(NodePtrSet, len(cutNodes))

	edgeCutoff := abs64(int64(float64(totalValue) * o.EdgeFraction))

	// Filter out nodes with cum value below nodeCutoff.
	if nodeCutoff > 0 {
		if callTree {
			if nodesKept := g.DiscardLowFrequencyNodePtrs(nodeCutoff); len(g.Nodes) != len(nodesKept) {
				droppedNodes = len(g.Nodes) - len(nodesKept)
				g.TrimTree(nodesKept)
			}
		} else {