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:ruipbarra...@sapo.pt] Enviado el: lunes, 10 de diciembre de 2018 11:27 Para: Subirana Cachinero, Isaac; r-help@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 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
