N-day Averages for Streamflow Duration Hydrographs
Closes #10 (closed).
This PR does some refactoring to create support for calculating n-day rolling averages for those historical percentiles. Adds tests to check this functionality, and documents an example.
The new documented example plot looks like the following:
The impact of the averaging is clearly visible in the historic percentile envelopes; the actual streamflow shown in the black lines is not averaged and is the daily values.