roll_median() produced incorrect
results in the presence of NAs. (#42)Properly document the align argument – the function
accepts “center” rather than “middle”. (#28)
Fixed an issue where empty fills were not handled correctly.
The interface has now been standardized such that each
implemented window function has version center-aligned by default
(e.g. roll_mean()), a left-aligned version
(roll_meanl()), and right-aligned version
(roll_meanr()).
Implement rolling window functions for mean(),
median(), min(), max(),
prod(), sum(), sd() and
var().