SmartIterator: Visual Analytics Workflows for Supervising Unsupervised Data Grouping

Unsupervised learning methods – topic modeling, partition-based and density-based clustering – produce data groupings without human guidance, yet choosing and evaluating those groupings should not itself be unsupervised. We present SmartIterator (SI), a visual analytics approach that treats the full sequence of grouping results across a parameter sweep as a first-class analytical object. For each method family, SI provides a structured six-phase workflow that guides the analyst through systematic exploration of grouping results – from quality-metric overview through transition-stability assessment, membership-confidence evaluation, content and context inspection, and recurrent-archetype verification to an informed decision – building cumulative understanding of data structure along the way. The workflows are operationalized through IteraScope (IS), a coordinated visual display combining quality-metric charts with semantic color encoding, a 1D group embedding with Sankey-style transition flows and violin plots of membership confidence, a 2D group embedding with HDBSCAN-detected recurrent archetypes that highlights iterations capturing all persistent patterns, and domain-specific linked views for contextualized interpretation. We demonstrate the three workflows on: (1) simulated social-media messages from the VAST Challenge 2011 (density-based clustering, validated against ground truth), (2) EU population statistics across $\sim {1 500}$ NUTS-3 regions (partition-based clustering), and (3) 30 years of IEEE VIS papers (NMF topic modeling). The workflows constitute the main contribution: they provide actionable, method-specific guidance for navigating parameter spaces, studying how data structure evolves across configurations, and grounding analytical understanding in domain context – yielding knowledge about the data that no single “best” result can provide.