[R] Does a formula object have a "left hand side"

[William Dunlap]

attr(terms(formula), "response") is 1 if
the formula has a left hand side and 0
otherwise.

At a lower level, you can look at
length(formula): 2 means there is no LHS,
3 means there is (any other value indicates
that someone made a call object that the
parser would not make).

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Erik Iverson
> Sent: Monday, December 13, 2010 12:17 PM
> To: R-help
> Subject: [R] Does a formula object have a "left hand side"
> 
> Hello,
> 
> Does anyone know of a function that will determine whether
> or not a formula object has a left hand side?
> 
> I.e., can differentiate between
> 
> y ~ x + z
> 
> and
> 
> ~ x + z
> 
> Perhaps I'm overlooking the obvious...
> 
> Thanks!
> 
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