  zoo is an R package providing an S3 class with methods for indexed totally
ordered observations, such as discrete irregular time series. Its key design
goals are independence of a particular index/time/date class and consistency
with base R and the "ts" class for regular time series. This paper describes
how these are achieved within zoo and provides several illustrations of the
available methods for "zoo" objects which include plotting, merging and
binding, several mathematical operations, extracting and replacing data and
index, coercion and NA handling. A subclass "zooreg" embeds regular time series
into the "zoo" framework and thus bridges the gap between regular and irregular
time series classes in R.
