merge.formula: Merge Formula With Right Hand Side of Second Formula
In lasso2: L1 Constrained Estimation aka `lasso'

This is method for formulas of the merge generic function. Here it is support for the function l1ce and not intended to be called directly by users.

1 2	## S3 method for class 'formula' merge(x, y, ...)

`x,y`	formulas.
`...`	potentially further arguments passed to methods.

merge(y ~ x1, ~ x2) ## ->  y ~ x1 + x2

f2 <- merge(y ~ x1*x2, z ~ (x2+x4)^3)
f. <- merge(y ~ x1*x2,   ~ (x2+x4)^3) # no LHS for 2nd term
f2
stopifnot(f2 == f.)

R Package to solve regression problems while imposing
	 an L1 constraint on the parameters. Based on S-plus Release 2.1
Copyright (C) 1998, 1999
Justin Lokhorst   <jlokhors@stats.adelaide.edu.au>
Berwin A. Turlach <bturlach@stats.adelaide.edu.au>
Bill Venables     <wvenable@stats.adelaide.edu.au>

Copyright (C) 2002
Martin Maechler <maechler@stat.math.ethz.ch>
y ~ x1 + x2
<environment: 0x1d59d30>
y ~ x1 * x2 + (x2 + x4)^3
<environment: 0x1d71788>