Time Series Visualization (I)

Basic tasks and visual strategies for temporal data

Befor beginning

Be careful of variation across datasets and variation across tasks
Based on that, there have been several efforts to systematically taxonomize the types of queries that time series visualizations have been used for.

Human eyes good at catching information of lines: use geom_line() to create basic lines
It is useful to draw area plot to emphasize the fact that these are amounts (they must be nonnegative). e.g. trade volume: use geom_area() to create area plot
For a larger collection of time series: use group_by() and facet_wrap() or facet_grid() to create plots at the same time
To clearly compare the y values of different sequences: use geom_tile() to create heatmap