Bulk Omics Clustering Analysis

Bulk Omics Clustering Analysis

Systematic workflow for clustering biological samples, features, or any quantitative data matrix. Implements multiple clustering algorithms with rigorous validation, comparison, and interpretation to identify meaningful data groupings.

When to Use This Skill

Use clustering analysis when you need to:

• ✅ Group biological samples by gene expression profiles (bulk RNA-seq, proteomics)
• ✅ Identify feature patterns (genes/proteins with similar expression across conditions)
• ✅ Discover subtypes in disease or treatment response groups
• ✅ Analyze trajectories in time-series or developmental data
• ✅ Quality control by detecting batch effects or outliers
• ✅ Compare methods by systematically evaluating multiple clustering approaches

Don't use this skill for:

• ❌ Single-cell RNA-seq clustering → Use scrnaseq-scanpy-core-analysis or scrnaseq-seurat-core-analysis
• ❌ Gene co-expression network analysis → Use coexpression-network

Key Concept: Clustering reveals natural groupings in data without prior labels. Different algorithms make different assumptions—this workflow helps you choose and validate the right approach for your data.

Language Support: This skill supports both Python and R implementations. Choose based on your preference and existing analysis pipeline. Python offers scikit-learn ecosystem integration; R offers ComplexHeatmap and rich Bioconductor tools.

Quick Start (5-Minute Example)

Test the workflow with the ALL (Acute Lymphoblastic Leukemia) dataset - 128 pediatric ALL patients with B-cell and T-cell subtypes:

R (Recommended for ALL dataset):

# 1. Load example data (ALL dataset from Chiaretti et al. 2004)
source("scripts/load_example_data.R")
data_list <- load_example_clustering_data()
data <- data_list$data
sample_names <- data_list$sample_names
feature_names <- data_list$feature_names
metadata <- data_list$metadata

# 2. Run clustering
source("scripts/hierarchical_clustering.R")
result <- hierarchical_clustering(data, n_clusters = 2)
cluster_labels <- result$cluster_labels
hclust_obj <- result$clustering_object

# 3. Visualize
source("scripts/plot_cluster_heatmap.R")
plot_cluster_heatmap(
  data,
  cluster_labels,
  output_dir = "quick_test_results"
)

# 4. Export results
# Results automatically saved by plotting functions
cat("\n✓ Quick start complete!\n")
cat(sprintf("Cell types: B-cell ALL (n=%d), T-cell ALL (n=%d)\n",
            sum(metadata$cell_type == "B"),
            sum(metadata$cell_type == "T")))

Python users: The Python implementation can use the same ALL dataset via rpy2, or use your own data. For ALL dataset examples in Python, you'll need pip install rpy2 and R installed. See full workflow below.

Expected output: Dendrogram distinguishing B-cell vs T-cell ALL, PCA plots, silhouette plots, heatmaps in quick_test_results/

Note: For your own data, follow the full workflow below with the Clarification Questions.

Installation

Language Choice

This workflow supports both Python and R. Choose one based on:

• Python: Better for large-scale data (>10k samples), integration with machine learning pipelines, modern plotting (plotnine)
• R: Better for heatmap visualization (ComplexHeatmap), Bioconductor integration, traditional bioinformatics workflows

You can also mix: use R for visualization (heatmaps) and Python for clustering algorithms.

Python Installation

Required Software

Optional: gap-stat (Apache 2.0), yellowbrick (Apache 2.0) - both permitted for commercial use

Minimum Python version: Python ≥3.8

License Compliance: All software packages use BSD-3-Clause, MIT, or similar permissive licenses that allow commercial use in AI agent applications.

R Installation

Minimum R version: R ≥4.0

Required packages: cluster, factoextra, NbClust, ComplexHeatmap, pheatmap, dendextend, dbscan, mclust, ggplot2, ggprism (all GPL/MIT licensed, commercial use permitted)

Quick install:

install.packages(c('cluster', 'factoextra', 'NbClust', 'pheatmap',
                   'dendextend', 'dbscan', 'mclust', 'ggplot2', 'ggprism'))
if (!require('BiocManager')) install.packages('BiocManager')
BiocManager::install('ComplexHeatmap')

Detailed R installation guide: references/r-quick-start.md#r-installation

Inputs

Required Input

1. Data Matrix (CSV, TSV, Excel, or HDF5):

• Sample clustering: Rows = samples, Columns = features (genes/proteins)
• Feature clustering: Rows = features, Columns = samples
• Values should be normalized and comparable (TPM, FPKM, VST, Z-scores)
• Missing values: handle by imputation or removal before clustering

2. Sample/Feature Metadata (CSV or TSV, optional but recommended):

• IDs matching data matrix rows/columns
• Annotations for validation (tissue type, condition, known groups)
• Used to interpret and validate clustering results

Data Requirements

• Minimum samples/features: 10+ (20+ recommended for robust clustering)
• Normalization: Required—use appropriate method for data type
• Batch effects: Remove or regress out before clustering
• Outliers: Identify and consider removing extreme outliers
• Dimensionality: High-dimensional data (>1000 features) benefits from PCA first

Supported Data Types

• Transcriptomics: Bulk RNA-seq (normalized counts, TPM, FPKM)
• Proteomics: Protein abundance data
• Metabolomics: Metabolite concentrations
• Multi-omics: Integrated features from multiple assays
• Clinical: Patient feature matrices
• Any quantitative matrix: General-purpose application

Outputs

Cluster assignments:

• clustering_assignments.csv - Sample/feature IDs with cluster labels
• clustering_statistics.csv - Size, centroids, and characteristics per cluster

Validation metrics:

• clustering_validation_metrics.json - Silhouette, Davies-Bouldin, Calinski-Harabasz scores
• stability_results.csv - Bootstrap resampling stability scores (if run)

Characterization:

• clustering_cluster*_features.csv - Top distinguishing features for each cluster (ANOVA/Kruskal-Wallis)
• clustering_all_cluster_features.csv - Combined features for all clusters

Analysis objects (pickle/RDS):

• clustering_analysis_object.pkl - Complete clustering object for downstream use
  • Load with: import pickle; obj = pickle.load(open('clustering_analysis_object.pkl', 'rb'))
  • Contains: linkage matrix (hierarchical), fitted model (k-means, GMM, HDBSCAN)
  • Required for: Advanced analysis, re-cutting dendrograms, model inspection
• clustering_data_matrix.csv - Normalized/transformed data matrix used for clustering

Visualizations (PNG + SVG at 300 DPI):

• Dendrogram (hierarchical clustering)
• PCA/UMAP scatter plots with cluster colors
• Silhouette plots
• Cluster heatmaps
• Cluster size barplots
• Optimal k determination plots (if run)

Supporting data:

• clustering_parameters.json - All parameters used in analysis

Clarification Questions

Before starting analysis, gather the following information:

1. Input Files (ASK THIS FIRST):

• Do you have specific gene expression or omics data file(s) to cluster?
• If you've uploaded a file, is it the data matrix (samples × features or features × samples) you'd like to analyze?
• Expected file types: CSV, TSV, Excel (.xlsx), HDF5 (.h5), or RDS (R data objects)
• Or use ALL (Acute Lymphoblastic Leukemia) example data? (Real patient data: 128 pediatric ALL samples with B-cell and T-cell subtypes, 1000 most variable genes. Dynamically loads from Bioconductor in ~30 seconds via scripts/load_example_data.R. Citation: Chiaretti et al. 2004. R recommended for this dataset.)

2. Which programming language do you prefer?

• Python: Modern ecosystem with scikit-learn, better for large datasets (>10k samples), machine learning integration
• R: Rich Bioconductor tools, excellent heatmap visualization (ComplexHeatmap), traditional bioinformatics workflows
• Both: Use Python for clustering algorithms, R for heatmap visualization (recommended for best of both worlds)
• No preference: Will use Python (default, more comprehensive scripts available)

3. What are you clustering?

• Samples (rows = samples, columns = features like genes)
  • Example: Group patients by gene expression profiles
• Features (rows = features, columns = samples)
  • Example: Group genes by expression patterns across conditions
• Both (explore both clustering directions)

4. What is your data format and normalization status?

• Bulk RNA-seq: TPM, FPKM, VST, rlog
• Proteomics: TMT/iTRAQ normalized intensities, LFQ
• Metabolomics: Normalized peak areas
• Already normalized: Z-scores, scaled values
• Raw data: Needs normalization (specify data type)

5. What clustering approach do you prefer?

• Hierarchical (recommended for exploration): Creates a tree-like dendrogram showing relationships at all scales. You can cut the tree at any height to get different numbers of clusters after seeing the structure. Best for visualization and when you don't know k. Deterministic (same results every run). Works well for small-medium datasets (<5k samples).
• K-means: Fast partitioning method that requires specifying k upfront. Best for large datasets (>5k samples) with spherical/compact clusters. Results may vary between runs, so use high n_init.
• Density-based (HDBSCAN): Automatically finds k by identifying dense regions. Can detect arbitrary cluster shapes and marks outliers. No need to specify k. Best when clusters have varying densities or you want outlier detection.
• Model-based (GMM): Probabilistic soft clustering where samples have membership probabilities for each cluster. Useful when clusters overlap or you need uncertainty estimates. Requires specifying k.
• Compare all methods: Systematic comparison (recommended for exploratory analysis)

6. Do you know the expected number of clusters (k)?

• Yes, k = [number]: Will validate this choice with quality metrics
• No, exploratory: Will test multiple k values (2-15) and help determine optimal k
• Approximate range: k between [min] and [max]
• Not needed: Hierarchical clustering lets you choose k later; HDBSCAN finds k automatically

7. What distance metric is most appropriate?

• Euclidean: Default for most continuous data
• Correlation: For gene expression (focuses on pattern similarity)
• Manhattan: Robust to outliers
• Cosine: For high-dimensional sparse data
• Unsure: Will use Euclidean (default)

8. Should we apply dimensionality reduction first?

• Yes, use PCA: Recommended for >1000 features
• Yes, use UMAP: For visualization and manifold learning
• No: Keep original feature space (<100 features)
• Both: PCA for clustering, UMAP for visualization

9. How should cluster quality be validated?

• Internal metrics only: Silhouette, Davies-Bouldin, Calinski-Harabasz
• Known labels available: Compare to known groups (adjusted Rand index)
• Stability analysis: Bootstrap resampling to test robustness
• Biological validation: Check for differential features between clusters

Standard Workflow

Note: Run from the OmicsClaw root directory and add the workflow scripts to sys.path:

import sys; import os; sys.path.insert(0, os.path.abspath('knowledge_base/scripts/bulk-omics-clustering'))

🚨 MANDATORY: USE SCRIPTS EXACTLY AS SHOWN - DO NOT WRITE INLINE CODE 🚨

Note: This skill requires decisions (algorithm, distance metric, k value) - adapt parameters to your data using guidance in references/decision-guide.md.

Step 1 - Load data:

For ALL example data (R recommended):

source("scripts/load_example_data.R")
data_list <- load_example_clustering_data()
data <- data_list$data
sample_names <- data_list$sample_names
feature_names <- data_list$feature_names
metadata <- data_list$metadata

For your own data (Python or R):

# Python
from prepare_data import load_and_prepare_data
data, sample_names, feature_names = load_and_prepare_data(
    "your_data.csv",
    normalize_method="zscore"
)

# R
source("scripts/prepare_data.R")
data_list <- load_and_prepare_data("your_data.csv", normalize_method = "zscore")
data <- data_list$data

DO NOT write custom data loading code. Use the provided functions.

Step 2 - Run clustering analysis:

# Choose ONE clustering method and run it:

# Option A: Hierarchical clustering (recommended for exploration)
from hierarchical_clustering import hierarchical_clustering
linkage_matrix, cluster_labels = hierarchical_clustering(
    data,
    n_clusters=2,  # For ALL dataset: B-cell vs T-cell; adjust for your data
    linkage_method="ward",
    distance_metric="euclidean"
)
clustering_object = linkage_matrix

# Option B: K-means clustering (fast, for large datasets)
from kmeans_clustering import kmeans_clustering
cluster_labels, kmeans_model = kmeans_clustering(
    data,
    n_clusters=2,  # For ALL dataset: B-cell vs T-cell; adjust for your data
    n_init=50
)
clustering_object = kmeans_model

# Option C: HDBSCAN (automatic k detection)
from density_clustering import hdbscan_clustering
cluster_labels, hdbscan_model = hdbscan_clustering(
    data,
    min_cluster_size=10
)
clustering_object = hdbscan_model

# Validate clustering quality
from cluster_validation import validate_clustering
validation_results = validate_clustering(data, cluster_labels, metrics="all")
print(f"Silhouette score: {validation_results['silhouette']:.3f}")

DO NOT write custom clustering code. Use one of the provided methods.

Step 3 - Generate visualizations:

# Generate comprehensive plots
from plot_clustering_results import plot_all_results
from dimensionality_reduction import apply_pca, apply_umap

# Optional: compute PCA/UMAP for visualization
pca_data = apply_pca(data, n_components=2)
umap_data = apply_umap(data, n_components=2)

# Create all plots
plot_all_results(
    data=data,
    cluster_labels=cluster_labels,
    sample_names=sample_names,
    feature_names=feature_names,
    pca_data=pca_data,
    umap_embedding=umap_data,
    linkage_matrix=clustering_object if 'linkage_matrix' in locals() else None,
    output_dir="clustering_results"
)

🚨 DO NOT write inline plotting code (matplotlib.pyplot.savefig, seaborn.clustermap, etc.). Use plot_all_results(). 🚨

The script handles PNG + SVG export with graceful fallback for optional dependencies.

Step 4 - Export results:

# Export all results including analysis objects for downstream use
from export_results import export_all

export_all(
    data=data,
    cluster_labels=cluster_labels,
    sample_names=sample_names,
    feature_names=feature_names,
    validation_results=validation_results,
    clustering_object=clustering_object,
    output_dir="clustering_results"
)

DO NOT write custom export code. Use export_all().

✅ VERIFICATION - You should see:

• After Step 1: "✓ Data loaded successfully!"
• After Step 2: "✓ Clustering completed successfully!"
• After Step 3: "✓ Plots saved to clustering_results"
• After Step 4: "=== Export Complete ==="

❌ IF YOU DON'T SEE THESE: You wrote inline code. Stop and use the scripts as shown.

⚠️ CRITICAL - DO NOT:

• ❌ Write inline clustering algorithms → STOP: Use provided clustering functions
• ❌ Write inline plotting code (matplotlib.pyplot.savefig, seaborn.clustermap, etc.) → STOP: Use plot_all_results()
• ❌ Write custom export code → STOP: Use export_all()
• ❌ Try to install plotting dependencies manually → scripts handle fallback automatically

⚠️ IF SCRIPTS FAIL - Script Failure Hierarchy:

1. Fix and Retry (90%) - Install missing package, re-run script
2. Modify Script (5%) - Edit the script file itself, document changes
3. Use as Reference (4%) - Read script, adapt approach, cite source
4. Write from Scratch (1%) - Only if genuinely impossible, explain why

NEVER skip directly to writing inline code without trying the script first.

For detailed parameter guidance and decision-making, see:

• Algorithm selection: references/decision-guide.md#algorithm
• Distance metrics: references/decision-guide.md#distance
• Optimal k: references/decision-guide.md#optimal-k

Common Issues

Debugging checklist:

1. Check data shape and missing values: data.shape, np.isnan(data).sum()
2. Verify normalization: Data should be comparable across features (z-scores, scaled)
3. Check cluster labels: Should range from 0 to k-1 (or include -1 for noise in HDBSCAN)
4. Validate with metrics: Silhouette >0.3 is decent, >0.5 is good
5. Inspect visually: PCA/UMAP plots should show clear groupings

Decision Guide

Make three critical decisions before clustering:

Comprehensive decision guidance: references/decision-guide.md

Common Patterns

Pattern 1: Sample Subtype Discovery - references/common-patterns.md#pattern-1 Pattern 2: Gene Co-clustering - references/common-patterns.md#pattern-2 Pattern 3: Method Comparison - references/common-patterns.md#pattern-3 Additional: QC/outlier detection, stability testing, batch validation - references/common-patterns.md

Suggested Next Steps

After completing clustering:

1. Differential Analysis - Use bulk-rnaseq-counts-to-de-deseq2 to identify cluster-specific signatures
2. Functional Enrichment - Use functional-enrichment-from-degs to interpret cluster biology
3. Refinement - If unclear: try different metrics, adjust k, remove outliers, use variable features subset

Related Skills

Prerequisite: bulk-rnaseq-counts-to-de-deseq2 (normalize RNA-seq data) Alternatives: scrnaseq-scanpy-core-analysis, scrnaseq-seurat-core-analysis (single-cell), coexpression-network Downstream: de-results-to-gene-lists, functional-enrichment-from-degs, de-results-to-plots

References

Reference documentation:

• references/decision-guide.md - Comprehensive decision guidance (algorithm, distance, k)
• references/common-patterns.md - Additional use case patterns
• references/clustering_methods_comparison.md - Algorithm selection guide
• references/validation_metrics_guide.md - Metric interpretation
• references/distance_metrics_guide.md - Distance metric selection
• references/parameter_guide.md - Parameter tuning details
• references/best_practices.md - Workflow best practices

Python scripts:

• scripts/prepare_data.py - Data loading and preprocessing
• scripts/distance_metrics.py - Distance calculations
• scripts/dimensionality_reduction.py - PCA, UMAP
• scripts/hierarchical_clustering.py - Hierarchical methods
• scripts/kmeans_clustering.py - K-means variants
• scripts/density_clustering.py - DBSCAN, HDBSCAN
• scripts/model_based_clustering.py - GMM
• scripts/optimal_clusters.py - Optimal k determination
• scripts/cluster_validation.py - Quality metrics
• scripts/stability_analysis.py - Bootstrap validation
• scripts/characterize_clusters.py - Feature importance
• scripts/plot_clustering_results.py - Visualizations
• scripts/export_results.py - Export functions

R scripts:

• scripts/hierarchical_clustering.R - Hierarchical clustering with dendextend
• scripts/plot_cluster_heatmap.R - ComplexHeatmap visualization (recommended for publication figures)
• Additional R implementations available upon request

Evaluation:

• eval/complete_example_analysis.py - Full workflow example

Online resources:

Python:

• scikit-learn clustering
• HDBSCAN documentation

R:

• factoextra clustering
• ComplexHeatmap vignettes
• dendextend tutorial

Key papers:

• Rousseeuw (1987) - Silhouettes for cluster validation
• Tibshirani et al. (2001) - Gap statistic
• McInnes et al. (2017) - HDBSCAN algorithm
• D'haeseleer (2005) - Clustering in genomics