2006-09-18 Sren Hjsgaard <sorenh@agrsci.dk>

	* summaryBy has been reimplemented. 

	* summaryBy takes . as argument on both lhs and rhs in formula

	* summaryBy, splitBy takes drop=FALSE argument (just like split
	does)

	* transformBy function has been added

2006-02-05 Sren Hjsgaard <sorenh@agrsci.dk>

	* sampleBy modified allow for also 'systematic samples',
	e.g. every 5th row.

	* summaryBy takes ... arguments to FUN. No default NA action is
	taken. 
	
2006-02-02 Sren Hjsgaard <sorenh@agrsci.dk>

	* A sampleBy function has been added.

	* A subsetBy function has been added.

2006-01-26 Sren Hjsgaard <sorenh@agrsci.dk>

	* Function summaryBy modified so one can write log(x) on the left
	hand side of '~'

	* Function summaryBy modified such that NAs are removed. What to
	do about Inf??
	
2006-01-17 Sren Hjsgaard <sorenh@agrsci.dk>

	* Function summaryBy modified to take . as lhs in formula and to
	take idvar = ~formula

	* Functions powerBy, histBy, qqnormBy have been removed (figure
	out how to do histBy and qqnormBy using xyplot() in lattice).
	