Supernovae Type Ia Classification — Phase 2 Tier 2

This branch, phase2-tier2-compact-feature-ablation, is the canonical Phase 2 Tier 2 branch for the project. It builds on the frozen Phase 2 Tier 1 compact 16-feature XGBoost baseline and explains why that compact model works through feature ablation, feature-block ablation, staged subset growth, reduced-core experiments, and supporting reproducibility artifacts.

The focus of this branch is not a new preprocessing pipeline. It reuses the Phase 2 Tier 1 processed SPCC/SNPhotCC feature table, compact feature set, fixed split protocol, and XGBoost evaluation setup so every Tier 2 result is directly comparable to the compact baseline.

Current Status

Phase 2 Tier 2 is complete as a reproducible analysis branch. The branch now includes:

• the Phase 2 Tier 1 compact 16-feature baseline reference,
• Tier 2 ablation and subset-growth experiment scripts,
• generated CSV, JSON, Markdown, PNG, and PDF artifacts under results/phase2_tier2/ and plots/phase2_tier2/,
• corrected compact-baseline PR and ROC curves for the 16-feature model,
• dataset, feature-dictionary, training-protocol, uncertainty, learning-curve, and artifact-index support files,
• and Zenodo archives for both the initial v1 package and the current v2 support package.

The current archived version of this branch is phase2-tier2-v2.0, which includes the normalized Phase 2 Tier 2 support package and updated branch documentation.

Baseline Reference

The frozen compact baseline comes from Phase 2 Tier 1 and uses 16 physically interpretable features. It is the reference point for all Tier 2 deltas.

Metric	Compact 16-feature baseline
F1	0.844230
ROC-AUC	0.976588
PR-AUC	0.927761

The corrected compact-baseline curve artifacts are:

results/phase2_tier1/phase2_tier1_compact_baseline_plots/phase2_tier1_compact_baseline_precision_recall_curve.png
results/phase2_tier1/phase2_tier1_compact_baseline_plots/phase2_tier1_compact_baseline_roc_curve.png

These curves belong to the Phase 2 Tier 1 compact baseline model, not the older original-paper model and not a separate Tier 2 model.

Compact Feature Set

The compact model uses four physical feature families.

Group	Features
Brightness	r_mean_flux, g_mean_flux, z_peak_flux, i_peak_flux, r_peak_flux
Color	peak_color_g_minus_r, peak_color_r_minus_i, peak_color_i_minus_z
Variability	i_std_flux, z_std_flux, r_std_flux, i_amplitude
Temporal	r_time_of_peak, i_time_of_peak, z_time_of_peak, time_span

Tier 2 Results

The main Tier 2 conclusion is that temporal information is the most decisive family for the compact classifier, while brightness, color, and variability provide complementary structure. The compact feature set can be reduced to a smaller interpretable core with only modest degradation, but the full compact set remains the strongest and most stable reference model.

Key generated results:

Analysis	Main output	Interpretation
Single-feature ablation	results/phase2_tier2/feature_ablation_metrics.csv	time_span is the strongest individual feature by F1 loss when removed.
Block ablation	results/phase2_tier2/block_ablation_metrics.csv	Removing temporal features causes the largest block-level degradation.
Subset growth	results/phase2_tier2/subset_growth_metrics.csv	Performance grows as brightness, color, variability, and temporal information are added.
Minimal core	results/phase2_tier2/minimal_core_metrics.csv	A 10-feature core retains most of the compact baseline performance.
Master report	results/phase2_tier2/phase2_tier2_report.md	Human-readable summary of the Tier 2 ablation results.

Highlights from results/phase2_tier2/phase2_tier2_report.md:

• Removing time_span gives the largest single-feature F1 drop: delta F1 = -0.033952.
• Removing the temporal block gives the largest block-level drop: delta F1 = -0.046596, delta PR-AUC = -0.054893.
• The best reduced core is the top-10 subset: F1 = 0.838509, PR-AUC = 0.916900.
• The full compact model remains the preferred reference: F1 = 0.844230, PR-AUC = 0.927761.

Figures

The primary Tier 2 figures are:

plots/phase2_tier2/feature_ablation_delta_f1.png
plots/phase2_tier2/block_ablation_delta_f1.png
plots/phase2_tier2/subset_growth_f1.png
plots/phase2_tier2/subset_growth_paper_ready.png
plots/phase2_tier2/minimal_core_tradeoff.png

The paper-ready subset-growth figure is:

plots/phase2_tier2/subset_growth_paper_ready.png

It uses the four cumulative stages:

1. brightness only,
2. brightness + color,
3. brightness + color + variability,
4. full compact model.

It plots both F1 and PR-AUC and is intended for the ablation/growth-of-information discussion.

Supporting Artifacts

Additional Phase 2 Tier 2 support material is stored under results/phase2_tier2/.

Important files include:

results/phase2_tier2/artifact_index.md
results/phase2_tier2/dataset_summary.md
results/phase2_tier2/training_protocol.md
results/phase2_tier2/compact_feature_dictionary.md
results/phase2_tier2/selected_compact_model.md
results/phase2_tier2/uncertainty_summary.md
results/phase2_tier2/learning_curve.md
results/phase2_tier2/validation_logloss_curve.md
results/phase2_tier2/tier2_experiment_audit.md

The artifact index is the best entry point for the full support package:

results/phase2_tier2/artifact_index.md
results/phase2_tier2/artifact_index.csv

Running The Workflow

Use the project environment defined by environment.yml or astro-ml.yml.

Example:

conda env create -f environment.yml
conda activate astro-ml

The Tier 2 scripts expect the processed Phase 2 Tier 1 compact dataset to exist:

data/processed/phase2_tier1_compact_baseline.csv

The core Tier 2 experiment order is:

python3 phase2_tier2_feature_ablation.py
python3 phase2_tier2_block_ablation.py
python3 phase2_tier2_subset_growth.py
python3 phase2_tier2_minimal_core.py
python3 phase2_tier2_summary.py

The support-artifact scripts can be run after the compact dataset and Tier 2 outputs are available:

python3 phase2_tier2_metadata.py
python3 phase2_tier2_training_protocol.py
python3 phase2_tier2_feature_dictionary.py
python3 phase2_tier2_selected_model.py
python3 phase2_tier2_uncertainty.py
python3 phase2_tier2_learning_curves.py
python3 phase2_tier2_example_light_curve.py
python3 phase2_tier2_audit.py
python3 phase2_tier2_artifact_index.py

To regenerate the corrected compact-baseline PR and ROC curves:

python3 phase2_tier1_compact_curves.py

Repository Structure

The current Phase 2 Tier 2 branch centers on these files and folders:

supernovae_classification/
├── README.md
├── data/
│   └── processed/
│       ├── phase2_tier1_compact_baseline.csv
│       └── spcc_features_tier1.csv
├── feature_pipeline/
├── plots/
│   └── phase2_tier2/
├── results/
│   ├── phase2_tier1/
│   └── phase2_tier2/
├── phase2_tier1_compact_curves.py
├── phase2_tier2_common.py
├── phase2_tier2_feature_ablation.py
├── phase2_tier2_block_ablation.py
├── phase2_tier2_subset_growth.py
├── phase2_tier2_minimal_core.py
├── phase2_tier2_summary.py
├── phase2_tier2_metadata.py
├── phase2_tier2_training_protocol.py
├── phase2_tier2_feature_dictionary.py
├── phase2_tier2_selected_model.py
├── phase2_tier2_uncertainty.py
├── phase2_tier2_learning_curves.py
├── phase2_tier2_example_light_curve.py
├── phase2_tier2_audit.py
└── phase2_tier2_artifact_index.py

Older Phase 1 and Phase 2 Tier 1 utilities remain in the repository for provenance, but this README documents the current Phase 2 Tier 2 branch state.

Release And DOI

The current Phase 2 Tier 2 Zenodo release is:

• Version: phase2-tier2-v2.0
• DOI: 10.5281/zenodo.19666153
• Zenodo record: https://zenodo.org/records/19666153
• GitHub tag: phase2-tier2-v2.0

Citation:

Anurag Garg. (2026). mranuraggarg/supernovae_classification:
Phase 2 Tier 2 v2: Compact Feature Ablation Support Package
(phase2-tier2-v2.0). Zenodo. https://doi.org/10.5281/zenodo.19666153

The previous Phase 2 Tier 2 Zenodo release is:

• Version: phase2-tier2-v1.0
• DOI: 10.5281/zenodo.19665796
• GitHub tag: phase2-tier2-v1.0

The DOI for all Zenodo versions of this project is:

• Concept DOI: 10.5281/zenodo.15074652

Data Source And Inspiration

This repository originally drew inspiration from Adam Moss's supernova classification work and data organization:

• Adam Moss's Supernovae Dataset

Phase 2 extends that direction by reconstructing a native SPCC/SNPhotCC preprocessing and feature-engineering workflow, then using compact physically interpretable features for controlled model analysis.

License

This project is licensed under the MIT License.