Write Accessible Alt Text

Generate accessible alt text for data visualizations and images in this project.

ARGUMENTS

• label: (optional) specific figure label or chunk to target
• file: (optional) specific file to process

Detect project type

Before proceeding, identify the project context and read the relevant reference. Check for a _pkgdown.yml file in the project root to detect a pkgdown site:

ls _pkgdown.yml 2>/dev/null && echo "pkgdown" || echo "not pkgdown"

• pkgdown site (_pkgdown.yml present) → read references/pkgdown.md
• Quarto documents (no _pkgdown.yml, .qmd files present) → read references/quarto.md

If the context is still ambiguous, ask the user which format they are working in.

Key advantage: source code access

Unlike typical alt text scenarios where you only see an image, we have access to the code that generates each chart. Use this to extract precise details:

From plotting code:

• Variable mappings → exact variable names for axes
• Color/fill mappings → what color encodes
• Plot type functions → scatter, histogram, line chart, etc.
• Trend lines or fitted curves → overlaid statistical fits
• Faceting/subplots → number of panels and what varies
• Color scales → encoding scheme (sequential, diverging, categorical)
• Axis labels and titles → customized labels

From data generation code:

• Random distributions → expected distribution shape
• Transformations → what was done to data
• Feature engineering → preprocessing applied
• Filtering/subsetting → what subset is shown

From surrounding prose:

• Text before/after the chunk explains the purpose and key insight
• Chapter context tells you what the figure is meant to teach
• This is often the best source for the "key insight" part of alt text

Three-part structure (Amy Cesal's formula)