Table 6. Top 10 most informative GC-MS chromatographic features with respect to the classification accuracy of the petroleum substances.
See S3–S5 Tables for the list of all chromatographic features and their respective ranks in each analysis.
| 3-Class prediction | 9-Class prediction | 16-Class prediction | ||||
|---|---|---|---|---|---|---|
| GC-MS Chromatographic Feature | Rank* | Mean decrease in accuracy (%)# | Rank | Mean decrease in accuracy (%) | Rank | Mean decrease in accuracy (%) |
| C4-Naphthalenes | 6 | 6.82 | 13 | 8.68 | 1 | 10.38 |
| Naphthobenzothiophene | 10 | 6.54 | 14 | 8.56 | 7 | 9.44 |
| C2-Naphthobenzothiophenes | 24 | 6.12 | 2 | 9.09 | 10 | 9.40 |
| Benzothiophene | 21 | 6.25 | 3 | 9.08 | 14 | 9.25 |
| C3-Phenanthrene/anthracenes | 5 | 6.90 | 6 | 8.86 | 33 | 8.55 |
| C4-Phenanthrene/anthracenes | 8 | 6.58 | 35 | 7.76 | 3 | 9.57 |
| Benzo(b)fluoranthene | 19 | 6.28 | 20 | 8.42 | 8 | 9.42 |
| Dibenzothiophene | 41 | 5.76 | 4 | 9.02 | 4 | 9.56 |
| C1-Dibenzothiophenes | 2 | 7.10 | 22 | 8.35 | 26 | 8.69 |
| Benzo(k)fluoranthene | 27 | 6.06 | 16 | 8.53 | 11 | 9.34 |
*Rank of the feature among 55 total for each classification analysis (3-, 9-, or 16-class prediction). Top 10 features with the overall highest rank in all three analyses were selected.
#Mean decrease in the accuracy of classification when this feature is removed from the analysis.