Visual Analytics - An Interaction of Sight and Thought - JMP

Multiple views of change through time
Have you ever noticed that time-series data can look quite different if you change the
interval of time that you’ve aggregated it to in a graph? For example, if you are
examining a year’s worth of visits to your website with one value per quarter
(aggregated to quarterly intervals), and then switch to a monthly aggregation of the
same data, and then switch to a daily aggregation, the patterns of change might look
quite different.
All three versions of the graph are useful and correct, but the daily version reveals
details that aren’t visible when viewing the same data by month or quarter. On the other
hand, the overall trend is difficult to discern from the daily view. One view isn’t better
than the other in general, but one is definitely better than the other when you have a
specific analytical purpose in mind. For this reason, don’t restrict your view of timeseries
data to a single interval of time, especially when looking for anything that seems
interesting. Switch the level of aggregation from year to quarter, quarter to month,
month to week, week to day, and so on—back and forth—to tease out the insights that
can only arise when this is done.
Software products that allow you to quickly and easily switch between various intervals
of time while viewing data graphically are what’s needed to encourage this practice. The
ability to switch time intervals with a mouse click or two, or by using something as
simple as an interval slider control, will set you free to explore without distraction from
onerous operations.