Chart Types & Data Visualization Reference
Choosing the right chart is the first step of data visualization. This page lists the most common chart types, when to use them and when to avoid them, so your data tells a clear story.
| Chart Type | Best For | Avoid When |
|---|---|---|
| Line Chart | Time series, trends, continuous data (stock price, traffic, temperature) | Unordered categories or single-point comparisons only |
| Bar Chart | Comparing values across distinct categories (sales by region, population by country) | Too many categories or showing part-to-whole ratios |
| Horizontal Bar Chart | Long category labels that read better horizontally | Time series or emphasizing trends |
| Pie Chart | Showing part-to-whole ratios with 5–7 categories or fewer | Many categories or similarly-sized slices |
| Donut Chart | Same as pie chart; center can show total or key metric | Precise comparison of segment sizes |
| Scatter Plot | Showing correlation between two continuous variables | Few data points or non-continuous variables |
| Area Chart | Emphasizing cumulative volume or magnitude over time | Overlapping series or precise reading |
Frequently Asked Questions
Should I use a bar chart or a line chart?
Look at the horizontal axis: if it is time or a continuous variable, use a line chart to emphasize trends. If it is discrete categories, use a bar chart to emphasize comparison. Never connect unordered categories with a line, because it implies a continuous change that does not exist.
Why should pie charts be used sparingly?
Human eyes are much worse at comparing angles and areas than lengths. When there are more than 5–7 slices or slices are similar in size, pie charts make it hard to judge proportions accurately. Use bar charts or tables instead.
What is the most important principle of data visualization?
Accuracy beats decoration: pick the chart type that most faithfully represents the data, remove unnecessary ornamentation (3D, shadows, gradients), and start the vertical axis at zero for bar charts to avoid visual distortion.
Can a line chart show many series?
Yes, but limit simultaneously visible series to 3–5. Too many crossing lines become unreadable. Split into small multiples or add interactive highlighting when needed.