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gh-k-dense-ai-claude-scient…/skills/scanpy/references/plotting_guide.md
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Scanpy Plotting Guide

Comprehensive guide for creating publication-quality visualizations with scanpy.

General Plotting Principles

All scanpy plotting functions follow consistent patterns:

  • Functions in sc.pl.* mirror analysis functions in sc.tl.*
  • Most accept color parameter for gene names or metadata columns
  • Results are saved via save parameter
  • Multiple plots can be generated in a single call

Essential Quality Control Plots

Visualize QC Metrics

# Violin plots for QC metrics
sc.pl.violin(adata, ['n_genes_by_counts', 'total_counts', 'pct_counts_mt'],
             jitter=0.4, multi_panel=True, save='_qc_violin.pdf')

# Scatter plots to identify outliers
sc.pl.scatter(adata, x='total_counts', y='pct_counts_mt', save='_qc_mt.pdf')
sc.pl.scatter(adata, x='total_counts', y='n_genes_by_counts', save='_qc_genes.pdf')

# Highest expressing genes
sc.pl.highest_expr_genes(adata, n_top=20, save='_highest_expr.pdf')

Post-filtering QC

# Compare before and after filtering
sc.pl.violin(adata, ['n_genes_by_counts', 'total_counts'],
             groupby='sample', save='_post_filter.pdf')

Dimensionality Reduction Visualizations

PCA Plots

# Basic PCA
sc.pl.pca(adata, color='leiden', save='_pca.pdf')

# PCA colored by gene expression
sc.pl.pca(adata, color=['gene1', 'gene2', 'gene3'], save='_pca_genes.pdf')

# Variance ratio plot (elbow plot)
sc.pl.pca_variance_ratio(adata, log=True, n_pcs=50, save='_variance.pdf')

# PCA loadings
sc.pl.pca_loadings(adata, components=[1, 2, 3], save='_loadings.pdf')

UMAP Plots

# Basic UMAP with clusters
sc.pl.umap(adata, color='leiden', legend_loc='on data', save='_umap_leiden.pdf')

# UMAP colored by multiple variables
sc.pl.umap(adata, color=['leiden', 'cell_type', 'batch'],
           save='_umap_multi.pdf')

# UMAP with gene expression
sc.pl.umap(adata, color=['CD3D', 'CD14', 'MS4A1'],
           use_raw=False, save='_umap_genes.pdf')

# Customize appearance
sc.pl.umap(adata, color='leiden',
           palette='Set2',
           size=50,
           alpha=0.8,
           frameon=False,
           title='Cell Types',
           save='_umap_custom.pdf')

t-SNE Plots

# t-SNE with clusters
sc.pl.tsne(adata, color='leiden', legend_loc='right margin', save='_tsne.pdf')

# Multiple t-SNE perplexities (if computed)
sc.pl.tsne(adata, color='leiden', save='_tsne_default.pdf')

Clustering Visualizations

Basic Cluster Plots

# UMAP with cluster annotations
sc.pl.umap(adata, color='leiden', add_outline=True,
           legend_loc='on data', legend_fontsize=12,
           legend_fontoutline=2, frameon=False,
           save='_clusters.pdf')

# Show cluster proportions
sc.pl.umap(adata, color='leiden', size=50, edges=True,
           edges_width=0.1, save='_clusters_edges.pdf')

Cluster Comparison

# Compare clustering results
sc.pl.umap(adata, color=['leiden', 'louvain'],
           save='_cluster_comparison.pdf')

# Cluster dendrogram
sc.tl.dendrogram(adata, groupby='leiden')
sc.pl.dendrogram(adata, groupby='leiden', save='_dendrogram.pdf')

Marker Gene Visualizations

Ranked Marker Genes

# Overview of top markers per cluster
sc.pl.rank_genes_groups(adata, n_genes=25, sharey=False,
                        save='_marker_overview.pdf')

# Heatmap of top markers
sc.pl.rank_genes_groups_heatmap(adata, n_genes=10, groupby='leiden',
                                 show_gene_labels=True,
                                 save='_marker_heatmap.pdf')

# Dot plot of markers
sc.pl.rank_genes_groups_dotplot(adata, n_genes=5,
                                 save='_marker_dotplot.pdf')

# Stacked violin plots
sc.pl.rank_genes_groups_stacked_violin(adata, n_genes=5,
                                        save='_marker_violin.pdf')

# Matrix plot
sc.pl.rank_genes_groups_matrixplot(adata, n_genes=5,
                                    save='_marker_matrix.pdf')

Specific Gene Expression

# Violin plots for specific genes
marker_genes = ['CD3D', 'CD14', 'MS4A1', 'NKG7', 'FCGR3A']
sc.pl.violin(adata, keys=marker_genes, groupby='leiden',
             save='_markers_violin.pdf')

# Dot plot for curated markers
sc.pl.dotplot(adata, var_names=marker_genes, groupby='leiden',
              save='_markers_dotplot.pdf')

# Heatmap for specific genes
sc.pl.heatmap(adata, var_names=marker_genes, groupby='leiden',
              swap_axes=True, save='_markers_heatmap.pdf')

# Stacked violin for gene sets
sc.pl.stacked_violin(adata, var_names=marker_genes, groupby='leiden',
                     save='_markers_stacked.pdf')

Gene Expression on Embeddings

# Multiple genes on UMAP
genes = ['CD3D', 'CD14', 'MS4A1', 'NKG7']
sc.pl.umap(adata, color=genes, cmap='viridis',
           save='_umap_markers.pdf')

# Gene expression with custom colormap
sc.pl.umap(adata, color='CD3D', cmap='Reds',
           vmin=0, vmax=3, save='_umap_cd3d.pdf')

Trajectory and Pseudotime Visualizations

PAGA Plots

# PAGA graph
sc.pl.paga(adata, color='leiden', save='_paga.pdf')

# PAGA with gene expression
sc.pl.paga(adata, color=['leiden', 'dpt_pseudotime'],
           save='_paga_pseudotime.pdf')

# PAGA overlaid on UMAP
sc.pl.umap(adata, color='leiden', save='_umap_with_paga.pdf',
           edges=True, edges_color='gray')

Pseudotime Plots

# DPT pseudotime on UMAP
sc.pl.umap(adata, color='dpt_pseudotime', save='_umap_dpt.pdf')

# Gene expression along pseudotime
sc.pl.dpt_timeseries(adata, save='_dpt_timeseries.pdf')

# Heatmap ordered by pseudotime
sc.pl.heatmap(adata, var_names=genes, groupby='leiden',
              use_raw=False, show_gene_labels=True,
              save='_pseudotime_heatmap.pdf')

Advanced Visualizations

Tracks Plot (Gene Expression Trends)

# Show gene expression across cell types
sc.pl.tracksplot(adata, var_names=marker_genes, groupby='leiden',
                 save='_tracks.pdf')

Correlation Matrix

# Correlation between clusters
sc.pl.correlation_matrix(adata, groupby='leiden',
                         save='_correlation.pdf')

Embedding Density

# Cell density on UMAP
sc.tl.embedding_density(adata, basis='umap', groupby='cell_type')
sc.pl.embedding_density(adata, basis='umap', key='umap_density_cell_type',
                        save='_density.pdf')

Multi-Panel Figures

Creating Panel Figures

import matplotlib.pyplot as plt

# Create multi-panel figure
fig, axes = plt.subplots(2, 2, figsize=(12, 12))

# Plot on specific axes
sc.pl.umap(adata, color='leiden', ax=axes[0, 0], show=False)
sc.pl.umap(adata, color='CD3D', ax=axes[0, 1], show=False)
sc.pl.umap(adata, color='CD14', ax=axes[1, 0], show=False)
sc.pl.umap(adata, color='MS4A1', ax=axes[1, 1], show=False)

plt.tight_layout()
plt.savefig('figures/multi_panel.pdf')
plt.show()

Publication-Quality Customization

High-Quality Settings

# Set publication-quality defaults
sc.settings.set_figure_params(dpi=300, frameon=False, figsize=(5, 5),
                               facecolor='white')

# Vector graphics output
sc.settings.figdir = './figures/'
sc.settings.file_format_figs = 'pdf'  # or 'svg'

Custom Color Palettes

# Use custom colors
custom_colors = ['#1f77b4', '#ff7f0e', '#2ca02c', '#d62728']
sc.pl.umap(adata, color='leiden', palette=custom_colors,
           save='_custom_colors.pdf')

# Continuous color maps
sc.pl.umap(adata, color='CD3D', cmap='viridis', save='_viridis.pdf')
sc.pl.umap(adata, color='CD3D', cmap='RdBu_r', save='_rdbu.pdf')

Remove Axes and Frames

# Clean plot without axes
sc.pl.umap(adata, color='leiden', frameon=False,
           save='_clean.pdf')

# No legend
sc.pl.umap(adata, color='leiden', legend_loc=None,
           save='_no_legend.pdf')

Exporting Plots

Save Individual Plots

# Automatic saving with save parameter
sc.pl.umap(adata, color='leiden', save='_leiden.pdf')
# Saves to: sc.settings.figdir + 'umap_leiden.pdf'

# Manual saving
import matplotlib.pyplot as plt
fig = sc.pl.umap(adata, color='leiden', show=False, return_fig=True)
fig.savefig('figures/my_umap.pdf', dpi=300, bbox_inches='tight')

Batch Export

# Save multiple versions
for gene in ['CD3D', 'CD14', 'MS4A1']:
    sc.pl.umap(adata, color=gene, save=f'_{gene}.pdf')

Common Customization Parameters

Layout Parameters

  • figsize: Figure size (width, height)
  • frameon: Show frame around plot
  • title: Plot title
  • legend_loc: 'right margin', 'on data', 'best', or None
  • legend_fontsize: Font size for legend
  • size: Point size

Color Parameters

  • color: Variable(s) to color by
  • palette: Color palette (e.g., 'Set1', 'viridis')
  • cmap: Colormap for continuous variables
  • vmin, vmax: Color scale limits
  • use_raw: Use raw counts for gene expression

Saving Parameters

  • save: Filename suffix for saving
  • show: Whether to display plot
  • dpi: Resolution for raster formats

Tips for Publication Figures

  1. Use vector formats: PDF or SVG for scalable graphics
  2. High DPI: Set dpi=300 or higher for raster images
  3. Consistent styling: Use the same color palette across figures
  4. Clear labels: Ensure gene names and cell types are readable
  5. White background: Use facecolor='white' for publications
  6. Remove clutter: Set frameon=False for cleaner appearance
  7. Legend placement: Use 'on data' for compact figures
  8. Color blind friendly: Consider palettes like 'colorblind' or 'Set2'
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