[R] repeating the same variable in formula

[peter dalgaard]

You might be looking for this:

> all.vars(~chol+age+age, unique=FALSE)
[1] "chol" "age"  "age" 


-pd


> On 10 Dec 2018, at 11:35 , Subirana Cachinero, Isaac <isubirana using imim.es> wrote:
> 
> Thank you for your response.
> In fact, I use the formula environament to select variables, as part of the code of another function.
> I would like to allow the user to select the same variable more than once.
> The use of I() may partly solve the problem. However, I would like attr(terms(g),"term.labels") would return a vector with as many components as variables including repetitions. And using I() function, there would be some work remaining to split "I(age + age)" into "age", "age", taking into account that in other examples variable may include white spaces or other characters within ` `.
> 
> Isaac.
> 
> -----Mensaje original-----
> De: Rui Barradas [mailto:ruipbarradas using sapo.pt] 
> Enviado el: lunes, 10 de diciembre de 2018 11:27
> Para: Subirana Cachinero, Isaac; r-help using r-project.org
> Asunto: Re: [R] repeating the same variable in formula
> 
> Hello,
> 
> The formulas
> 
> y ~ cholesterol + age + age
> 
> and
> 
> y ~ cholesterol + age
> 
> are the same formula.
> If you want 'age' twice, maybe
> 
> g <- y ~ cholesterol + I(age + age)
> attr(terms(g), "term.labels")
> #[1] "cholesterol"  "I(age + age)"
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
> Às 06:49 de 10/12/2018, Subirana Cachinero, Isaac escreveu:
>> y ~ cholesterol + age + age
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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