[R] Help with functions as arguments
Rainer M Krug
r.m.krug at gmail.com
Tue Feb 12 09:38:19 CET 2013
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On 12/02/13 08:30, Ian Renner wrote:
> Hi,
>
> I am trying to write a function which defines some arguments, then uses those arguments as
> arguments of other function calls. It's a bit tricky to explain, so a simple example will have
> to suffice. I imagine this has a simple solution, but perusing through environments and other
> help lists has not helped. Suppose I have two functions:
>
>
> f1 = function(a) { b = a + 1 b } f2 = function(x, z) { y = x*z -2 y }
>
> Where I am running into trouble is when I want to call function f1 within function f2:
>
> f2(x = 3, z = f1(x))
>
> This returns the error:
>
> "Error in f1(x) : object 'x' not found"
Obviously easiest:
X <- 3
f2(X=x, Z=f1(X))
Your solution does not work, as the f1(x) is evaluated and the value is passed on to f1, and your
x is an argument and *only in the function f2* available (= in this context *no* assignment).
I remember something similar, and the solution had to do with eval() and quote() and friends -
i.e. you have to only evaluate f(x) *inside* the function f2 - but unfortunately I do not remember
details.
Cheers,
Rainer
>
> I'm not sure how to define environments within the functions so that the just-defined 'x' may
> be passed as an argument to f1 within f2.
>
> Any help would be greatly appreciated!
>
> Ian Renner [[alternative HTML version deleted]]
>
>
>
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