[R] programming questions

[Erik Iverson]

ivo welch wrote:
> quick programming questions.  I want to "turn on" more errors.  there
> are two traps I occasionally fall into.
> 
> * I wonder why R thinks that a variable is always defined in a data frame.
> 
>      > is.defined(d)
>      [1] FALSE
>      > d= data.frame( x=1:5, y=1:5 )
>      > is.defined(d$z)
>      [1] TRUE
>      > is.defined(nonexisting$garbage)
>      [1] TRUE

Which package/version of R is the 'is.defined' function in?

I don't seem to have it here on 2.11.1, which I know is not
the latest version of R.

What does 'defined' mean?

> 
> this is a bit unfortunate for me, because subsequent errors become
> less clear.   right now, I need to do '(is.defined(d) and
> !is.null(d$z))' to check that my function inputs are valid.  It would
> be nicer if one could just write "if (is.defined(d$z)".

"z" %in% names(d) ?

> 
> * is there a way to turn off automatic recycling?  I would rather get
> an error than unexpected recycling.  I can force recycling with rep()
> when I need to.
> 
> regards,
> 
> /iaw
> 
> ----
> Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)
> 
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