[R] substitute question

[Thomas Lumley]

On Thu, 18 Mar 2004, Gabor Grothendieck wrote:

>
> Tony, Thomas.  Thanks for your help.  Your comments were very
> useful.
>
> Unfortunately, my next step gives me a new round of problems.
>
> The following is the same as the last example except that instead
> of hard coding the function into the expression I wanted to
> pass it to the expression.  It seems like one has to do a double
> substitute to get this effect but I am having problems getting this
> to work.
>

The problem is that f is a function, not an expression. You need to work
with body(f)

Either
> f<-function(){a+1}>
body(f)<-do.call("substitute",list(body(f),list(a=quote(b))))> f
function ()
{
    b + 1
}

or
> f<-function(){a+1}
> body(f)<-eval(substitute(substitute(expr,list(a=quote(b))),list(expr=body(f))))
> f
function ()
{
    b + 1
}


	-thomas