Thanks for your replies.
I use the following script:
if(!exists(i)) stop ("set the variable i", call. = FALSE)
but before the stop expression, Error gets displayed:
Error: set the variable i
Is there another function that stops the execution, prints an expression
without printing Error or any other expression except the expression parameter?
Best,
--- On Fri, 9/11/09, Marc Schwartz <marc_schwa...@me.com> wrote:
From: Marc Schwartz <marc_schwa...@me.com>
Subject: Re: [R] how to determine if a variable is already set?
To: "carol white" <wht_...@yahoo.com>
Cc: r-h...@stat.math.ethz.ch
Date: Friday, September 11, 2009, 10:21 AM
On Sep 11, 2009, at 12:15 PM, carol white wrote:
> Hi,
> It might be a primitive question but how it is possible to determine if a
> variable is initialized in an environment? Suppose that we start a R session
> and wants to run a script which use the variable i. Which function could
> evaluate if i is already initialized or not and if not, then ask
> interactively the user to set it? This is to avoid the error message: object
> i is not found.
>
> Regards,
>
> Carol
See ?exists
Note that this will tell you if the object exists, not if it contains a
specifically desired initial value. You would have to check for the latter
after determining that the object does indeed exist.
HTH,
Marc Schwartz
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