[R] Using substitute in nested function calls

[Eik Vettorazzi]

Hi Sebastian,
how about this:

mycurve <- function (expr) {
do.call(curve,list(substitute(expr),-100,100))
}

mycurve(x^2)
mycurve(sin(x/20))
mycurve(x+x^2-x^3)

cheers

Am 21.02.2012 06:28, schrieb Sebastian Kranz:
> Dear List members,
> 
> I really, like the feature that one can call R functions with 
> mathematical expressions, e.g.
> 
> curve(x^2, 0, 1)
> 
> 
> I wonder, how I can construct in a simple way a function like
> 
> mycurve = function (expr) {...}
> 
> such that that a call
> 
> mycurve(x^2)
> 
> has the same effect as the call
> 
> curve(x^2, -100,100)
> 
> Below is some code that works, but it seems much to complicated: it 
> first substitutes and deparses the expression, creates a string with the 
> new function call and then parses and evaluates the string again. Does 
> anybody know a simpler, more elegant solution?
> 
> mycurve = function(expr) {
>    # The following attempt does not work
>    # curve(substitute(expr),-100,100)
> 
>    # Transform original expression to a string
>    org.expr = deparse(substitute(expr))
>    # Construct a string, parse it and evaluates it
>    eval(parse(text=paste("curve(",org.expr,",-100,100)",sep="")))
> }
> mycurve(x^2)
> 
> Best regards,
> Sebastian
> 
> 	[[alternative HTML version deleted]]
> 
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Eik Vettorazzi
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