Using elastic net regression to perform spectrally relevant variable selection
Bibliographic record
Abstract
Abstract Multivariate data such as spectra frequently contain measured variables that are uninformative, and removal of such variables requires the use of methods that can be used to select informative variables. Partial least squares (PLS) regression may incorporate information from uninformative measured variables, and so it is important to select variables before performing the PLS regression. Elastic net (EN) regression can be used to perform variable selection automatically. An EN regression can be used to select groups of correlated variables or to select either sparse or nonsparse sets of variables. However, the predictive performance of the EN regression can be significantly worse than competing 1‐step variable selection methods such as variable importance in projection (VIP). In the present work, the use of the EN to select variables, followed by conventional PLS regression on the selected variables (EN‐PLS), has been investigated. Variable selection by using EN‐PLS was compared with that from EN regression, sparse PLS regression, VIP, and from selectivity ratio selection on 2 data sets of visible/near‐infrared spectra. In all cases, the wavelengths selected were compared with reference data. The variables selected by using EN‐PLS offered advantages in interpretability and gave more robust prediction performance as compared with those obtained from full‐spectrum PLS and the other variable selection methods. This paper reports a method for variable selection by using an EN regression prior to a second regression by using PLS, a 2‐step method termed EN‐PLS. Variables selected by using EN‐PLS are compared with variables selected from the EN regression, as well as VIP, selectivity ratio, and the sparse PLS regression, 3 commonly used methods for variable selection in chemometrics. The EN‐PLS is shown to select variables that were more easily interpreted. In addition, EN‐PLS performed more robustly than a PLS regression performed on all variables, as well as reduced PLS regressions by using variables selected from either the sparse PLS regression algorithm or a VIP variable selection followed by PLS modeling.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".