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11-Aug-2018 New paper describes octave plots for visualizing alpha diversity.

12-Jun-2018 New paper shows that one in five taxonomy annotations in SILVA and Greengenes are wrong.

18-Apr-2018 New paper shows that taxonomy prediction accuracy is <50% for V4 sequences.

05-Oct-2017 PeerJ paper shows low accuracy of closed- and open-ref. QIIME OTUs.

22-Sep-2017 New paper shows 97% threshold is wrong, OTUs should be 99% full-length 16S, 100% for V4.

UPARSE tutorial video posted on YouTube. Make OTUs from MiSeq reads.



Taxonomy confidence measures

See also
  SINTAX algorithm
  Naive Bayesian Classifier algorithm
  sintax command
  nbc_tax command

The sintax and nbc_tax commands generates taxonomy predictions with confidence estimates specified by bootstrapping.

The definition and interpretation of a taxonomy prediction confidence estimate is not as simple as it might appear. Ideally, the error rate of predictions with confidence 0.9 should be approximately 10%, but in practice the error rate depends on the query dataset and on unknown characteristics of the reference dataset. This is shown by the simple example of a single query sequence -- the average accuracy will be 1.0 or 0.0, regardless of the confidence reported by the classifier.

References (please cite)
R.C. Edgar (2016), SINTAX: a simple non-Bayesian taxonomy classifier for 16S and ITS sequences, https://doi.org/10.1101/074161
  • SINTAX taxonomy prediction algorithm

  • Fast and simple method, accuracy comparable to RDP Classifier

R.C. Edgar (2018), Accuracy of taxonomy prediction for 16S rRNA and fungal ITS sequences, PeerJ 6:e4652
  • Cross-validation by identity, novel benchmark strategy enabling realistic accuracy estimates

  • Genus accuracy of best methods is 50% on V4 sequences

  • Recent algorithms do not improve on RDP Classifier or SINTAX

R.C. Edgar (2018), Taxonomy annotation and guide tree errors in 16S rRNA databases, PeerJ 6:e5030
  • Approx. one in five SILVA and Greengenes taxonomy annotations are wrong

  • SILVA and Greengenes trees have pervasive conflicts with type strain taxonomies