Regression model evaluation metrics

regression-model-evaluation-metrics

Summary

Compute and interpret performance metrics on held-out test data for continuous-value regression models, such as CCS prediction from molecular features. This skill ensures trained models generalize beyond training and validation sets by quantifying prediction accuracy across multiple statistical measures.

When to use

After training a deep-learning regression model (e.g., for CCS prediction from voxel projected area features), evaluate it on held-out test data to report per-molecule predictions and aggregate performance metrics. Apply this skill whenever you need to validate model accuracy on unseen molecules and generate publishable performance reports.

When NOT to use

• Input is already a feature table without ground-truth labels — metrics require paired predictions and reference values.
• Test data was not held out during training or hyperparameter tuning — evaluation will be overly optimistic and not reflect generalization.
• Model output is categorical or probabilistic rather than continuous — use classification metrics (accuracy, F1, AUC) instead.

Inputs

• trained PyTorch neural network model (checkpoint file)
• test dataset (SMILES, adduct type, ground-truth CCS labels)
• computed test features (voxel projected area, molecular graph, m/z, adduct encoding)

Outputs

• per-molecule CCS predictions (numerical values)
• regression performance metrics (MAE, RMSE, R², MRE)
• model performance summary report (aggregated statistics)

How to apply

Load the trained PyTorch model and the held-out test dataset (containing molecular features: voxel projected area, molecular graph, adduct one-hot encoding, m/z, and ground-truth CCS labels). Feed test features through the model to generate per-molecule CCS predictions. Compute standard regression metrics: mean absolute error (MAE), root mean squared error (RMSE), coefficient of determination (R²), and optionally mean relative error (MRE). Report predictions alongside metrics to assess both individual prediction quality and overall model generalization. Inspect residuals (predicted − actual) for systematic bias or heteroscedasticity.

Related tools

• PyTorch (Load trained regression model checkpoint and compute batch predictions on test data) — https://pytorch.org/
• pandas (Organize test features, ground-truth labels, and predicted CCS values into DataFrames for metric computation and export) — https://pandas.pydata.org/
• NumPy (Compute regression metrics (MAE, RMSE, R²) and residual analysis via vectorized operations) — https://numpy.org/
• scikit-learn (Provide standard regression metrics functions (mean_absolute_error, mean_squared_error, r2_score))

Examples

from PACCS.Prediction import PACCS_predict; PACCS_predict(input_path='data/external_test_set.csv', model_path='trained_model.pth', output_path='test_predictions.csv')

Evaluation signals

• R² value is positive and close to 1 (>0.8 typical for well-fit models); negative R² indicates model performs worse than a simple mean baseline
• MAE and RMSE are in physically plausible units (Ångströms² for CCS); compare against literature benchmarks and external test set performance
• Per-molecule prediction residuals (actual − predicted) are normally distributed with mean near zero; systematic bias or heteroscedasticity suggests model deficiency
• Test set metrics are comparable to validation metrics from training; large gap suggests overfitting
• External test set predictions (if available) show similar accuracy to curated dataset test fold, confirming generalization

Limitations

• Metrics are computed only on the held-out test set; performance on new, real-world molecules may differ if they have different chemical distributions.
• Single-fold evaluation does not capture variance across random seeds or data splits; k-fold or repeated-hold-out evaluation is more robust.
• RMSE is sensitive to outlier predictions; MAE may be more interpretable for applications with extreme values.
• R² can be misleading for non-linear relationships or when prediction errors are systematically biased in certain input regions.
• README mentions 8:1:1 split (training:validation:test) but does not specify random seed or stratification strategy, affecting reproducibility.

Evidence

• [other] Evaluate the trained model on held-out test data and output per-molecule CCS predictions alongside model performance metrics.: "Evaluate the trained model on held-out test data and output per-molecule CCS predictions alongside model performance metrics."
• [readme] The curated dataset is randomly split into the training, validation, and test sets in a ratio of 8:1:1.: "The curated dataset is randomly split into the training, validation, and test sets in a ratio of 8:1:1."
• [other] Train the model on the prepared dataset using PyTorch, optimizing for CCS prediction accuracy across epochs with appropriate loss function and learning rate scheduling.: "Train the model on the prepared dataset using PyTorch, optimizing for CCS prediction accuracy across epochs"
• [readme] The predicted CCS values of molecules are obtained by feeding the voxel projected area, molecular graph, one-hot encoding of adduct type, and m/z into the already trained PACCS model: "The predicted CCS values of molecules are obtained by feeding the voxel projected area, molecular graph, one-hot encoding of adduct type, and m/z into the already trained PACCS model"