Concept Map #2: Choosing Chart Types

STAT 80B - Data Visualization

Author

Dr. Marcela Alfaro Córdoba

What You’re Creating

A concept map or decision tree that helps you (and others) choose the right chart type for different data visualization scenarios. Think of it as a guide you’d give to someone asking “What kind of chart should I make?”

What’s a Concept Map?

A visual diagram that shows:

  • Boxes or nodes = concepts or chart types (like “bar chart,” “scatter plot,” “histogram”)
  • Lines with arrows = connections or decision paths between concepts
  • Labels on lines/nodes = decision criteria or relationships (like “if categorical,” “if showing distribution,” “when comparing”)

This can take the form of:

  • A decision tree (flowchart style with yes/no questions)
  • A concept map (network of connections showing relationships)
  • A hybrid (whatever works best for you to organize the information!)

Required Topics

Your map must help users choose charts for these four major purposes:

1. Amounts

Showing quantities or counts

Chart types to include:

  • Bar charts (simple, grouped, stacked)
  • Dot plots
  • Heatmaps

Decision criteria:

  • Number of categories
  • Need to compare across groups?
  • Want to show parts of a whole?

2. Distributions

Showing how data are spread out

Chart types to include:

  • Histograms
  • Density plots
  • Box plots
  • Violin plots
  • Strip plots

Decision criteria:

  • One variable or comparing groups?
  • Need to see individual points?
  • Showing outliers important?
  • Shape of distribution matters?

3. Proportions

Showing parts of a whole

Chart types to include:

  • Pie charts (and when NOT to use them!)
  • Stacked bar charts
  • Mosaic plots
  • Treemaps

Decision criteria:

  • Simple proportions or nested categories?
  • How many categories?
  • Need exact values or general sense?
  • Single dataset or comparing across groups?

4. Relationships

Showing associations between variables

Chart types to include:

  • Scatter plots
  • Line graphs
  • Bubble charts
  • Correlograms/correlation matrices
  • Connected scatter plots (for paired data)

Decision criteria:

  • How many variables?
  • Time series or not?
  • Paired/before-after data?
  • Looking for trends or correlations?
  • Overplotting an issue?

What to Include

Your concept map must contain:

1. Decision Points

Questions or criteria that lead to different chart choices:

  • What type of data? (categorical, quantitative, time)
  • How many variables? (1, 2, 3+)
  • What’s the purpose? (compare, show distribution, show relationship, show composition)
  • How many data points? (few, moderate, many)
  • Any special structure? (paired data, time series, hierarchical)

2. Chart Types

At least 12-15 different chart types distributed across the four major purposes (amounts, distributions, proportions, relationships)

3. When to Use / Avoid

For at least 3-4 chart types, include:

  • When this chart works well
  • When to avoid it (limitations)

Example:

Pie Chart
✓ Works: 2-5 categories, simple proportions
✗ Avoid: Many categories, precise comparisons needed, 
         multiple datasets

Decision Criteria to Consider

Think about these factors when building your map:

Data Type

  • Categorical (nominal vs ordinal)
  • Quantitative (continuous vs discrete)
  • Time/temporal
  • Geographic/spatial

Number of Variables

  • Single variable (univariate)
  • Two variables (bivariate)
  • Three+ variables (multivariate)

Purpose/Question

  • Compare values across categories
  • Show distribution or spread
  • Reveal relationship or correlation
  • Track change over time
  • Show composition (parts of whole)
  • Display ranking or order

Data Structure

  • Independent observations
  • Paired/matched data
  • Time series
  • Hierarchical/nested
  • Groups or clusters

Practical Constraints

  • Number of categories/groups
  • Number of data points
  • Need for precise values vs. general patterns
  • Audience expertise level

How to Make It

Step 1: Brainstorm

Write down:

  • All chart types you know from class
  • Decision questions that differentiate them
  • Examples you remember

Step 2: Organize

Group related charts together:

  • Which charts serve similar purposes?
  • What makes you choose one over another?
  • What are the major decision points?

Step 3: Structure

Decide on your format:

  • Decision tree: Start with “What’s your data type?” and branch from there
  • Concept map: Cluster by purpose (amounts, distributions, etc.) and show connections
  • Hybrid: Use both approaches where they make sense

Step 4: Connect and Label

  • Draw connections between concepts
  • Label every connection/branch clearly
  • Use phrases like:
    • “If categorical, use…”
    • “Works when…”
    • “Better for…”
    • “Choose this when…”
    • “If more than 5 categories…”

Step 5: Review

Ask yourself:

  • Can someone else follow my logic?
  • Did I cover all four main purposes?
  • Are my decision criteria clear?
  • Did I include examples?
  • Is it legible?

Format Requirements

  • Hand-drawn on standard paper (8.5” × 11”)
  • 1-2 pages maximum (use front and back if needed)
  • Legible and organized - you’ll need to scan or photograph it
  • Use pen or dark pencil so it scans clearly
  • Your name must be on the first page

Grading Rubric

Your concept map will be graded on:

Completeness (35%)

  • All four purposes covered (amounts, distributions, proportions, relationships)
  • At least 12-15 chart types included
  • Decision criteria present and relevant

Logic and Connections (30%)

  • Clear decision paths or logical groupings
  • Connections are labeled meaningfully
  • Criteria actually differentiate between chart types
  • Makes sense to follow the map to reach a chart choice

Depth (20%)

  • Goes beyond just naming charts
  • Includes “when to use” and “when to avoid” for some charts
  • Considers practical constraints (N size, number of categories, etc.)
  • Shows understanding of the principles behind chart selection

Clarity and Presentation (15%)

  • Organized and easy to follow
  • Legible text and clear visual structure
  • Good use of space (not too cramped)
  • Professional appearance

Total: 5 points

Submission Instructions

Creating Your Digital Copy

  1. Use your phone or scanner to create a clear image
  2. Make sure all text is readable
  3. Check that nothing is cut off
  4. Convert to PDF if multiple pages

Canvas Submission

  • Upload your PDF to Canvas assignment page
  • Deadline: Friday, February 13th at 11:59 PM
  • No extensions available - start early!
  • File naming: LastName_FirstName_ConceptMap2.pdf

Before You Submit

✓ Did you include your name?

✓ Is everything readable in the scan/export?

✓ Did you cover all four purposes?

✓ Do you have 12+ chart types?

✓ Are your decision criteria labeled clearly?

✓ Is the file size reasonable?

✓ Did you save it as PDF?

Tips for Getting Unstuck

If you’re overwhelmed:

  1. Start with the four main purposes as your top level
  2. Pick one purpose and list 3-4 chart types
  3. Write one decision question that picks between them
  4. Repeat for other purposes
  5. Then look for connections across purposes

If you’re not sure what to include:

  • Review the Wilke “Directory of Visualizations”
  • Look through your lab assignments
  • Think about charts you’ve seen in news/reports
  • Browse examples online for inspiration (but create your own map!)

Final Reminders

Why This Matters

This assignment helps you:

  • Organize your knowledge of chart types
  • Develop decision-making skills for real projects
  • Create a reference you can use for future work
  • Think critically about visualization choices
  • Prepare for your final project chart selection

Good luck! Remember: The goal is to create something useful, not something perfect. Focus on clear decision logic and you’ll do great!

Frequently Asked Questions

Can I include more than the required chart types?

Yes! More coverage is great, as long as you maintain clarity and organization.

What if I want to create this digitally but I’m not good at design software?

Keep it simple! we want ONLY hand-drawn maps.

Can I use chart types we haven’t covered in class yet?

Sure, but you’re not required to. Focus on what we’ve learned, but if you know about a chart type from outside class, you can include it!

How detailed should my decision criteria be?

Specific enough to actually make a decision. “Use bar chart for amounts” isn’t enough. “Use bar chart when you have categorical data and want to compare quantities across 2-10 categories” is better!

Can I work with a partner?

You can discuss ideas with classmates, but everyone must create and submit their own unique concept map. No two maps should be identical.

What if my map doesn’t fit on one page?

You can use front and back (= 2 pages). If you absolutely need more space, you can use a second sheet, but try to keep it concise. A cluttered 2-page map may score lower than a clear 1-page map!

Will you provide feedback on drafts?

If you bring a draft to office hours, I’m happy to give general feedback on organization and completeness. But I won’t “pre-grade” your work.

Is this graded on artistic ability?

No! It’s graded on content, logic, and clarity. Stick figures and basic boxes with arrows are totally fine. Focus on the thinking, not the art.

Still have questions? Post on the Ed discussion board or visit office hours!