Size is a very useful dimension for attracting the viewer’s attention toward certain points and away from other points. Size is an easy dimension for people to process and grasp, even when other dimensions are being used.
Size allows all feature types but is best with numerical features given the continuous nature of the representation. Categorical features can also be used with Size, but for the viewer to be able to differentiate between them, the feature would need to contain very few unique values. Even in this case, the viewer will not know intuitively which size represents which categorical value.
Size settings are found by switching to the Settings tab and selecting the Other button:
- Normalization – Numerical only, see Normalization
- Scale – Adjusts the size of all points to be either bigger or smaller. Note: This setting can be changed even when there is no feature mapped to size
- Range – Numerical only, filters out points outside of the two selected values