version      date  description
1.0      06/12/09  The first version on CRAN
2.0      07/13/09  Various bugs fixed; R2 plot implemented
2.1      09/14/09  Implemented sparse matrix improvements
3.0      04/29/11  Various functionalities added
3.1      08/22/11  More functionalities added
3.1.1    09/18/11  Bug in medsens weights fixed; damaged PDFs fixed
3.1.2    09/19/11  Fixed wrong plots in the vignette
3.1.3	 11/21/11  Import inconsistency with Matrix fixed
4.0      03/20/12  Design and multimed functions added, along with other new features
4.0.1    04/20/12  Bug in mediate.ced fixed, along with new example data