[R] Help with functions as arguments

[Rainer M Krug]

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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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