combine_rare_levels: Combines rare levels of a categorical variable
In regclass: Tools for an Introductory Class in Regression and Modeling

Description Usage Arguments Details Author(s) References Examples

This function takes a categorical variable and combines all levels with frequencies less than a user-specified threshold named Combined

1	combine_rare_levels(x,threshold=20,newname="Combined")

`x`	a vector of categorical values
`threshold`	levels that appear a total of `threshold` times or fewer will be combined into a new level called `Combined`
`newname`	defaults to `Combined`, but give the option as to what this new level will be called

Returns a list of two objects:

values - The recoded values of the categorical variable. All levels which appeared threshold times or fewer are now known as Combined combined - The levels that have been combined together

If, after being combined, the newname level has threshold or fewer instances, the remaining level that appears least often is combined as well.

Adam Petrie

Introduction to Regression and Modeling

	data(EX6.CLICK)
	x <- EX6.CLICK[,15]
	table(x)
	
	#Combine all levels which appear 700 or fewer times (AA, CC, DD)
	y <- combine_rare_levels(x,700)
  table( y$values )
  
  #Combine all levels which appear 1350 or fewer times.  This forces BB (which
  #occurs 2422 times) into the Combined level since the three levels that appear
  #fewer than 1350 times do not appear more than 1350 times combined
	y <- combine_rare_levels(x,1350)
  table( y$values )