**5. Computational aspects**

The technical performance of Excel-based animations is markedly influenced by the technique that is used to update the content of the worksheet cells. In particular, the computational time can be reduced considerably, if large arrays are updated by a single command rather than by creating a loop in which individual cells are updated one by one. The performance can also be improved by turning off the automatic screen updating and the automatic calculation of worksheets during parts of the execution of the animation macro.

The design of the markers in the bubble chart is yet another factor that strongly influences the computational time. It takes longer to update large bubbles than small markers, and more elaborate bubbles that resemble 3D balls can greatly retard the animation.

Test runs using a dataset comprising 10,000 cases showed that a chart with 400 highlighted bubbles could be updated in less than two seconds on a standard PC. If the dataset is substantially larger, it may be preferable to base the animation on a (random) sample of the original data.
