2. xts - extensible time series - Provide for uniform handling of R's different time-based data classes, maximizing native format information preservation and allowing for user level customization and extension, while simplifying cross-class interoperability.
3. data.table - data.table never has row names, uses setkey()
i can be expression of column names - 'where'
j can be expression of column names - 'select'
i can be data.table - binary search to DT's key in O(log n) time
Development Status: 5 - Production/Stable [Filter]
Intended Audience: Developers [Filter] , System Administrators [Filter]
License: GNU General Public License (GPL) [Filter]