How to read a line chart

Line charts show how a measure changes across a continuous dimension—usually time. They answer: Is it going up or down? Where are the peaks and dips?

What is a line chart?

A line chart plots points along an axis and connects them with lines. The x-axis is usually time or another continuous dimension; the y-axis is a measure. One or more series can be shown with different colors. The line emphasizes continuity and change.

When to use it

Use a line chart when you have continuous or sequential data (especially time) and want to show trend, rate of change, or compare a few series over the same dimension—e.g. revenue by month, traffic by day. Avoid it for unordered categories (use a bar chart) or for part-to-whole (use pie or stacked bar).

How to read it

Read the axes: typically time or sequence on the horizontal axis, measure on the vertical. Follow each line: slope up = increase, down = decrease. Use the legend to tell series apart. Look at peaks, troughs, and turning points. If the y-axis does not start at zero, note that small changes can look large.

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