create_relational.R

create_relational <- function( df, col, id_col="join_id", join_name="join_name" ) {
	if( !is.factor(df[,col]) )
		df[,col] <- as.factor(df[,col])
	
	df[,id_col] <- unclass( df[,col] )
	join_table <- data.frame( x=attr(unclass(df[,col]),"levels") )
	names(join_table) <- join_name
	join_table[,id_col] <- 1:length(attr(unclass(df[,col]),"levels"))
	join_table[,join_name] <- as.character( join_table[,join_name] )
	return( list(df=df, join_table=join_table) )
}