[R] Arguments of a function

[Gabor Grothendieck]

Normally one designs their function to input a formula in such a case
rather than design it to take the names directly.  Thus:

f <- function(formula = ~ x1 + x2) {
  xs <- c(x1 = 1, x2 = exp(1), x3 = 2*pi)
  v <- all.vars(formula)
  stopifnot(length(v) == 2, all(v %in% names(xs)))
  sum(xs[v])
}

# test
f()
f(~ x1 + x2) # same
f(~ x2+x3)


On Fri, Jan 8, 2010 at 1:15 PM, Lisa <lisajca at gmail.com> wrote:
>
> Dear all,
>
> I have a question about how to set arguments in my own function. For
> example, I have a function that looks like this:
>
> my.f <- function(a = x1, b = x2)
> {
>   x1 = equation 1
>   x2 = equation 2
>   x3 = equation 3
>   y = a + b
> }
>
> x1, x2, and x3 are temporary variables (intermediate results) calculated
> from other variables within the funciton. I want to use two of these three
> variables to calculate y, and write R script as below:
>
> my.f(a = x1, b = x2)
>
> or
>
> my.f(a = x2, b = x3)
>
> The error information shows that: “objects 'x1', 'x2', or 'x3' not found”.
>
> Can anybody help me solve this problem? Thanks in advance.
>
> Lisa
>
> --
> View this message in context: http://n4.nabble.com/Arguments-of-a-function-tp1009883p1009883.html
> Sent from the R help mailing list archive at Nabble.com.
>
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