On 10/5/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote:
> Given this:
>
> x1 <- "pred"
> x2 <- "lat"
> e <- expression(1+2*pred+3*lat)
>
> Try this:
>
> L <- list(as.name("x1"), as.name("x2"))
> names(L) <- c(x1, x2)
> do.call(substitute, list(e, L)) # e & L are evaluated first
>
> or perhaps:
>
> f <- e
> f <- sub("pred", "x1", f) # also converts to character
> f <- sub("lat", "x2", f)
> parse(text = sub("lat", "x2", f)) # convert back to expressionThe last line was supposed to be just: parse(text = f) > > > On 10/5/07, Ronaldo Reis Junior <[EMAIL PROTECTED]> wrote: > > Hi, > > > > I try to use a substitute function to generalise a equation. > > > > I have this: > > > > expression(1+2*pred+3*lat) > > > > I need to define the equation in function of x1 and x2 variables. Also I try > > to define who is x1 and x2. I try this: > > > > X1 <- "pred" > > X2 <- "lat" > > > > Now I need substitute pred and lat in equation by x1 and x2 defined on X1 > > and > > X2 above, I try this way: > > > > > > > substitute(expression(1+2*pred+3*lat),list(as.name(X1)=as.name(x1),as.name(X2)=as.name(x2)) > > Error: unexpected '=' > > in "substitute(expression(1+2*pred+3*lat),list(as.name(X1)=" > > > > My expected result is: > > > > expression(1 + 2 * x1 + 3 * x2) > > > > Any help? > > Thanks > > Ronaldo > > -- > > > Prof. Ronaldo Reis Júnior > > | .''`. UNIMONTES/Depto. Biologia Geral/Lab. de Biologia Computacional > > | : :' : Campus Universitário Prof. Darcy Ribeiro, Vila Mauricéia > > | `. `'` CP: 126, CEP: 39401-089, Montes Claros - MG - Brasil > > | `- Fone: (38) 3229-8187 | [EMAIL PROTECTED] | [EMAIL PROTECTED] > > | http://www.ppgcb.unimontes.br/ | ICQ#: 5692561 | LinuxUser#: 205366 > > > > ______________________________________________ > > R-help@r-project.org mailing list > > 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. > > > ______________________________________________ R-help@r-project.org mailing list 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.
