To add a trend line in Numbers on your Mac, select the chart, open the Series tab in the Format sidebar, expand Trendlines, and choose a line type from the pop-up menu. Numbers supports trendlines on bar, line, scatter, bubble, column, and area charts. You can also display the trendline’s equation or R-squared value. Apple’s Mac guide to trendlines

Add a trendline to an existing chart

  1. Open your spreadsheet in Numbers and click the chart. If the Format sidebar is hidden, click Format in the toolbar to show it.
  2. In the sidebar, click Series.
  3. Click the disclosure arrow beside Trendlines to expand its controls.
  4. Click the trendline pop-up menu and choose a type. The line appears on the chart for the selected data series.
  5. To see the fitted equation or R-squared value, select Show Equation or Show R² Value in the Trendlines controls. To label the line, select Name and enter a name; Numbers uses that name for all trendlines on the chart.

The chart must be editable. If you can’t change its settings, check whether it is locked; Apple notes that a locked chart must be unlocked before editing. If you have multiple series, pay attention to which series you selected: trendline controls appear in the Series tab, so make sure the intended data series is active before choosing the line type. Apple’s Mac guide to chart markings

Choose a chart that fits the data

Numbers lets you add trendlines to several chart types, but the chart should still match the question your data answers. A scatter chart is useful when you want to examine how one numeric measure relates to another: it plots paired values as points. For example, put the independent measurement in one column and the value you want to compare in another, then create a scatter chart from those columns. Apple’s guide says that with two selected columns, the first supplies the x-axis values and the second supplies the y-axis values. Apple’s guide to scatter and bubble charts

A line chart may suit values ordered across time or another sequence. In either case, make sure the chart’s plotted series contains the data you actually want to summarize. If the current chart type is unsuitable, select it, click the Chart tab in the Format sidebar, then choose another option from Chart Type. Apple’s guide to changing a chart’s type

Read the line and its statistics carefully

A trendline summarizes the overall direction of the selected data; it does not explain why the values move that way. The equation describes the displayed fit in terms of the chart’s variables. R-squared is a statistic associated with that fit, so it should be interpreted in the context of the data and the model type you selected. Neither a line nor a high R-squared value, by itself, establishes cause or guarantees that the pattern will continue.

Use the line as a visual aid alongside the original points or values. If the data bend, cluster, contain unusual values, or cover only a narrow range, a single trendline may conceal meaningful variation. Check the underlying table and axes before drawing a conclusion. This is practical interpretation guidance: Apple documents the controls for displaying the equation and R-squared value, but those controls do not certify that a chosen model is appropriate for a particular dataset.

Change or remove the trendline

To change the line’s appearance, click the trendline so white dots appear at its ends, then use the Stroke and Shadow controls in the sidebar. To remove it, click the chart, select the trendline, open the Trendline Options pop-up menu in the sidebar, and choose None. These steps remove the visual overlay while leaving the chart’s data in place, according to Apple’s instructions.

If the trendline controls are missing, first confirm that a chart is selected and that you are viewing Series rather than Chart or Axis settings. Then check that the chart is one of the supported types and that it can be edited. Once the intended series and line are visible, use the result as a concise summary of the data’s direction, not as a substitute for inspecting the observations.

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