Data Visualization Principles Cheat Sheet

Guides chart type selection, design best practices like data-ink ratio and consistent color encoding, and common mistakes that mislead viewers.

1 PageBeginnerFeb 25, 2026

A Clean Chart in Matplotlib

Remove chartjunk and emphasize the data itself.

python

import matplotlib.pyplot as pltfig, ax = plt.subplots(figsize=(8, 5))ax.bar(categories, values, color="#4C72B0")ax.spines["top"].set_visible(False)   # remove chartjunkax.spines["right"].set_visible(False)ax.set_title("Revenue by Region", fontsize=14, weight="bold")ax.set_ylabel("Revenue ($M)")ax.grid(axis="y", alpha=0.3)          # subtle gridlines onlyplt.tight_layout()plt.savefig("chart.png", dpi=150)

Choosing a Chart Type

Match the chart to the question you're answering.

Comparison (categories)- Use bar charts; sort bars by value unless there's a natural category order
Trend over time- Use line charts; keep the time axis continuous and evenly spaced
Part-to-whole- Use stacked bar or 100% stacked bar; avoid pie charts with more than 5 slices
Distribution- Use histograms or box plots to show spread, skew, and outliers
Relationship- Use scatter plots for two continuous variables; add a trend line for correlation
Ranking- Use horizontal bar charts sorted descending when category labels are long

Design Best Practices

Habits that make charts easier to read correctly.

Data-ink ratio- Maximize the proportion of ink used to show data vs. decoration (Tufte's principle)
Consistent color encoding- Use the same color for the same category across all charts in a report
Direct labeling- Label lines/bars directly instead of relying solely on a legend when possible
Start bar charts at zero- Truncated y-axes on bar charts exaggerate differences and mislead viewers
Pre-attentive attributes- Use color, size, or position (not just labels) to highlight the key takeaway

Pro Tip

Before choosing a chart type, write down the one-sentence takeaway you want the viewer to walk away with - the chart type should make that sentence obvious at a glance.

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