What key contains the labels. The value of each label key will be the X tick values if group by keys or the legend if group by labels.
In this example dataset:
Size | Red | Green | Blue |
---|---|---|---|
Small | 5 | 10 | 15 |
Medium | 25 | 30 | 35 |
Large | 50 | 60 | 70 |
The label key would be Size
Ensure the label key is not also selected in "Keys" as it will cause duplicate columns and break some visualisations.