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

[Phil Spector]

Erik -
    Perhaps the "response" attribute of the terms() function?

> formula1 = formula(y ~ x + z)
> formula2 = formula(~x + z)
> attr(terms(formula1),'response')
[1] 1
> attr(terms(formula2),'response')
[1] 0

    Although there may be more direct ways.

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Mon, 13 Dec 2010, Erik Iverson wrote:

> 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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