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name: create-viz description: > Create a data visualization such as a chart, graph, or plot tailored to the data and the message to convey. TRIGGER when: user asks to "create a chart", "plot this", "make a graph", "visualize this data", "bar chart", "line chart", "scatter plot", "heatmap", "histogram", or any specific chart type request. argument-hint: " <chart_type>" user-invocable: true

Data Visualization Creator

You are an expert data visualization designer. When the user asks you to create a chart, graph, or plot, follow this structured process.

Step 1: Understand the Message

Before choosing a chart type, answer:

1. What question does the visualization answer? (e.g., "How do sales compare across regions?")
2. Who is the audience? (technical, executive, general public)
3. What action should the viewer take? (compare, track, identify outliers, understand distribution)
4. How many dimensions are involved? (1D, 2D, 3D, multi-dimensional)

Step 2: Chart Type Selection Matrix

Relationship	Chart Type	Variables	Best Library
Change over time	Line chart	1 numeric + 1 time	plotly, matplotlib
Comparison	Bar chart	1 numeric + 1 categorical	plotly, seaborn
Proportion	Pie / donut (< 6 slices)	1 numeric + 1 categorical	plotly
Proportion (many)	Treemap	1 numeric + 1+ categorical	plotly
Distribution (1 var)	Histogram	1 numeric	seaborn, plotly
Distribution (compare)	Box / violin plot	1 numeric + 1 categorical	seaborn
Correlation	Scatter plot	2 numeric	plotly, seaborn
Correlation matrix	Heatmap	N numeric	seaborn
Ranking	Horizontal bar	1 numeric + 1 categorical	plotly
Part-to-whole over time	Stacked area	1 numeric + 1 time + 1 categorical	plotly
Geographic	Choropleth / bubble map	numeric + location	plotly, folium
Flow / process	Sankey diagram	source + target + value	plotly
Hierarchical	Sunburst	multiple categorical + 1 numeric	plotly
Relationship network	Network graph	nodes + edges	networkx + plotly

Step 3: Visual Encoding Principles

Position (most accurate)

• Use x/y position for the most important variable
• Time always goes on the x-axis (left to right)

Length (second most accurate)

• Bar length for comparison; always start bars at zero

Color

• Sequential: Light to dark for continuous data (e.g., viridis, blues)
• Diverging: Two-hue scale for data with a meaningful midpoint (e.g., RdBu)
• Categorical: Distinct hues for categories (max 8-10 colors)
• Highlight: Gray for context, one accent color for the focal data

Size

• Bubble size for a third numeric dimension; always include a legend

Shape

• Use sparingly; max 4-5 distinct shapes

Step 4: Implementation Standards

Title and Labels

Title:    Descriptive, answers "what does this show?" (not "Figure 1")
Subtitle: Additional context, time period, or data source
X-axis:   Label with units
Y-axis:   Label with units
Legend:    Clear names, not column codes

Formatting Rules

• Remove chart junk: no 3D effects, no unnecessary gridlines, no decorative elements
• Use commas in large numbers (1,000,000 not 1000000)
• Format percentages to 1 decimal (12.3%)
• Format currency with symbol and appropriate precision ($1.2M)
• Use consistent date formats (2026-01-15 or Jan 15, 2026)

Color Palettes (Recommended)

Palette	Use Case	Colors
Qualitative	Categorical data	Tab10, Set2, Pastel1
Sequential	Ordered numeric	Viridis, Blues, YlOrRd
Diverging	Deviation from center	RdBu, PiYG, Spectral
Color-blind safe	Always preferred	Viridis, Cividis, Okabe-Ito

Step 5: Code Templates

Plotly (Interactive)

import plotly.express as px

fig = px.bar(df, x="category", y="value", color="group",
             title="Clear Descriptive Title",
             labels={"category": "Category Name", "value": "Value ($)"},
             template="plotly_white")
fig.update_layout(
    font=dict(size=14),
    title_font_size=20,
    legend_title_text="Group",
    xaxis_tickangle=-45
)
fig.show()

Matplotlib/Seaborn (Publication-quality)

import matplotlib.pyplot as plt
import seaborn as sns

fig, ax = plt.subplots(figsize=(10, 6))
sns.barplot(data=df, x="category", y="value", hue="group", ax=ax)
ax.set_title("Clear Descriptive Title", fontsize=16, fontweight="bold")
ax.set_xlabel("Category Name", fontsize=12)
ax.set_ylabel("Value ($)", fontsize=12)
ax.legend(title="Group")
plt.tight_layout()
plt.show()

Step 6: Annotation and Storytelling

Add annotations to guide the viewer:

• Call out the key finding with an annotation arrow or text box
• Highlight the most important data point with a contrasting color
• Add reference lines for targets, averages, or benchmarks
• Use direct labels on lines/bars when fewer than 7 series (avoids legend lookup)

Quality Checklist

• Chart type matches the data relationship
• Title clearly states what the chart shows
• Axes are labeled with units
• Color palette is color-blind accessible
• No chart junk (3D, unnecessary gridlines, decorative elements)
• Numbers are formatted appropriately
• Legend is clear and does not overlap data
• Font sizes are readable (minimum 12px for labels)
• Aspect ratio is appropriate (not distorted)
• Source data is cited if applicable

Edge Cases

• Too many categories (> 15): Show top-N + "Other", or use a treemap
• Very long labels: Use horizontal bar chart or abbreviate with tooltip for full name
• Zero and negative values: Ensure bar chart starts at zero; use diverging bars for negatives
• Sparse data: Use scatter with jitter, not line chart; note gaps
• Dual y-axes: Avoid if possible; use separate panels (facets) instead
• Overplotting: Use transparency (alpha), jitter, hex bins, or contour plots
• Single data point: Show as annotated marker; do not draw a line