title: Feature combination networks for the interpretation of statistical machine learning models: application to Ames mutagenicity.
abstract: BACKGROUND
  A new algorithm has been developed to enable the interpretation of black box models. The developed algorithm is agnostic to learning algorithm and open to all structural based descriptors such as fragments, keys and hashed fingerprints. The algorithm has provided meaningful interpretation of Ames mutagenicity predictions from both random forest and support vector machine models built on a variety of structural fingerprints.A fragmentation algorithm is utilised to investigate the model's behaviour on specific substructures present in the query. An output is formulated summarising causes of activation and deactivation. The algorithm is able to identify multiple causes of activation or deactivation in addition to identifying localised deactivations where the prediction for the query is active overall. No loss in performance is seen as there is no change in the prediction; the interpretation is produced directly on the model's behaviour for the specific query.
  
  
  RESULTS
  Models have been built using multiple learning algorithms including support vector machine and random forest. The models were built on public Ames mutagenicity data and a variety of fingerprint descriptors were used. These models produced a good performance in both internal and external validation with accuracies around 82%. The models were used to evaluate the interpretation algorithm. Interpretation was revealed that links closely with understood mechanisms for Ames mutagenicity.
  
  
  CONCLUSIONS
  This methodology allows for a greater utilisation of the predictions made by black box models and can expedite further study based on the output for a (quantitative) structure activity model. Additionally the algorithm could be utilised for chemical dataset investigation and knowledge extraction/human SAR development.
authors.affiliation: Lhasa Limited, Granary Wharf House, 2 Canal Wharf, Holbeck, Leeds LS11 5PY UK. samuel.webb@lhasalimited.org.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Webb
authors.forename: Thierry
authors.initials: T
authors.lastname: Hanser
authors.forename: Brendan
authors.initials: B
authors.lastname: Howlin
authors.forename: Paul
authors.initials: P
authors.lastname: Krause
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Vessey