[R] how to determine if a variable is already set?

[Henrik Bengtsson]

Not the most beautiful solution: start your message with carriage return, e.g.

> stop("\rA long enough message");
A long enough message
> stop("\rfoo");
fooor:

/H

On Mon, Sep 14, 2009 at 5:06 PM, Bert Gunter <gunter.berton at gene.com> wrote:
> I don't believe the solution proposed below works and anyway misses the
> whole point of tryCatch(), which is **not** to test manually:
>
> f <- function(i){
>  val <- tryCatch(get("i"), error = function(e)"input error")
>  val ## can test val and carry on if not an error
> }
>
> ## testit
>
>> f()
> [1] "input error"
>> f(2)
> [1] 2
>>
>
> Bert Gunter
> Genentech Nonclinical Biostatistics
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
> Behalf Of Henrique Dallazuanna
> Sent: Monday, September 14, 2009 12:44 PM
> To: carol white
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] how to determine if a variable is already set?
>
> Try this:
>
> if (!exists("i"))
>   tryCatch(stop(""),
>          error = function(e)invisible(),
>            finally=print("Please set the i variable"))
>
> On Mon, Sep 14, 2009 at 3:38 PM, carol white <wht_crl at yahoo.com> wrote:
>
>> Thanks to your replies.
>>
>> In fact, the problem doesn't come from "exists" but from "stop" that
>> displays Error even if call. = FALSE. To answer to Dan, I quoted the
>> pramater of exists. So when the variable is not defined, stop displays the
>> expression message preceded by "Error". So the question was how not to
>> display "Error" or if there is another function that does stop's job
> without
>> displaying "Error"?
>>
>> Cheers,
>>
>> --- On Sun, 9/13/09, Michael Knudsen <micknudsen at gmail.com> wrote:
>>
>> From: Michael Knudsen <micknudsen at gmail.com>
>> Subject: Re: [R] how to determine if a variable is already set?
>> To: "carol white" <wht_crl at yahoo.com>
>> Cc: r-help at stat.math.ethz.ch
>> Date: Sunday, September 13, 2009, 7:06 AM
>>
>> On Fri, Sep 11, 2009 at 7:15 PM, carol white <wht_crl at yahoo.com> wrote:
>>
>> > It might be a primitive question but how it is possible to determine if
> a
>> variable is initialized in an environment?
>>
>> What about this?
>>
>> > "x" %in% ls()
>> [1] FALSE
>> > x = 41
>> > "x" %in% ls()
>> [1] TRUE
>>
>> Best,
>> Michael
>>
>> --
>> Michael Knudsen
>> micknudsen at gmail.com
>> http://lifeofknudsen.blogspot.com/
>>
>>
>>
>>
>>         [[alternative HTML version deleted]]
>>
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
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>>
>
>
>
> --
> Henrique Dallazuanna
> Curitiba-Parana-Brasil
> 250 25' 40" S 490 16' 22" O
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>