zoo: S3 Infrastructure for Regular and Irregular Time Series (Z's Ordered Observations)
Achim Zeileis, Gabor Grothendieck, Jeffrey A. Ryan · 2004
An S3 class with methods for totally ordered indexed observations. It is particularly aimed at irregular time series of numeric vectors/matrices and factors. zoo's key design goals are independence of a particular index/date/time class and consistency with ts and base R by providing methods to extend standard generics.