I'm working with a time series of choropleth maps showing the same indicator for the same administrative boundaries, but spanning period of nine years.
What would be the most appropriate strategy of designing class breaks for such a time series?
At the moment, I think the quintiles division would serve the purpose the best, since it allows to scan quickly for 20% of areas with highest/lowest values (for instance).
That works for one map, however I''m not sure how to porperly choose a scheme for time series.
Options that I came up with so far would be:
- use class intervals created separately for each map - advantage being they reflect the data structure for each year; disatvantage - harder to compare the maps between years.
- use class intervals of quintiles from the summary map for the whole time period (without yearly split of the underlying data) - advantage being easier comparison of the maps for each year; disadvantage - breaks might not be ideal in certain years.
- use class intervals of quintiles taken from the whole distribution of the data - all areas+all years - advantages disadvantages will most likely be simmilar to the above scenario.
What are your thoughts?