Delta Comparisons
A delta comparison shows the change between two data points in a table: between two scenarios, two periods, two dimension levels such as two products, or two nodes.
Overview
Comparisons are added to an existing table in the chart editor. Which method you choose matters more than it looks, because two of them disagree whenever the base value is negative.
Adding a comparison
- Create a table chart. Setting Nodes as rows, with Years and Scenarios as columns, is a good starting point.
- In the chart editor, add a comparison. Pick the two values to compare, then set the Calculation type.
- For a Delta, which is labeled YoY when you compare years, choose one of the three delta methods from the table below. CAGR is a calculation type of its own and is offered only when the two values are years.
The same comparison can be built across time, across dimension levels, for example sales for different products, and across nodes.
Editing existing comparisons
Once a table has at least one comparison, you can edit or remove comparisons in place.
- In the chart editor, open Edit Comparisons. The button appears only when the table already has a comparison.
- The dialog lists every comparison on the left. Select one to load its full configuration on the right, pre-filled with its current settings.
- Rename or reconfigure the comparison. You can edit as many comparisons as you like in the same session.
- To remove a comparison, use the trash icon next to it in the list.
- Click Save to apply all your changes at once. Cancel discards them; if you have unsaved changes, you are asked to confirm first.
Comparisons keep their position in the chart, and Save stays disabled until every edited comparison is valid.
Comparison methods
| Method | What it calculates | Formula |
|---|---|---|
| Absolute | The plain difference between the two data points. | second value - first value |
| Relative, default | The relative percentage change, carrying the sign of the absolute change. | abs((second value / first value) - 1) × signum(second value - first value) |
| Relative, simple | The plain percentage difference. | (second value / first value) - 1 |
| CAGR | The compound annual growth rate: the average growth needed over the given years to reach the second value. Offered only when the two data points are years. | abs(abs(second value / first value) ^ (1 / years) - 1) × signum(second value - first value) |
Choosing between the two relative comparisons
On a positive base the two agree. They diverge on a negative base, and that is the whole reason the default exists.
Going from -100 to -50 is an improvement of 50:
- Relative, simple returns
(-50 / -100) - 1 = -0.5, so -50 %, which reads as a decline. - Relative, default takes the size of that change and applies the sign of the absolute change:
abs(-0.5) × signum(50) = +0.5, so +50 %.
Use the default relative comparison unless you have a specific reason not to. The simple one is only safe when every base value is positive.
Related
- Formatting Charts: sorting, scales and table styles.
- Data Display in Charts and Tables: choosing what a table shows, and at which level of aggregation.
- KPI Charts: a comparison shown as a single figure rather than a table column.