Thank you for your time, Don. Exactly what I was looking for - a one-liner.
Feedback from others on this post has been good to expand my knowledge, though.
I'm too old for homework but have just started using R if/else, loops, and
functions and trying to get the hang of them. Best wishes - B

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-----Original Message-----
From: MacQueen, Don [mailto:macque...@llnl.gov]
Sent: Wednesday, September 21, 2016 11:26 AM
To: Crombie, Burnette N <bcrom...@utk.edu>; r-help@r-project.org
Subject: Re: [R] if/else help
Hopefully this is not a homework question.
The other responses are fine, but I would suggest the simplest way to do
exactly what you ask is
if (!exists('r4')) r4 <- data.frame(a=0, b=0, c=0, d='x')
The exists() function requires a character string for its first argument, i.e.,
the name of the object, not the object itself (check the help page for exists).
Using "get" to get it doesn't make sense if it already exists.
-Don
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
On 9/20/16, 12:31 PM, "R-help on behalf of Crombie, Burnette N"
<r-help-boun...@r-project.org on behalf of bcrom...@utk.edu> wrote:
>If a data.frame (r4) does not exist in my R environment, I would like
>to create it before I move on to the next step in my script. How do I
>make that happen? Here is what I want to do from a code perspective:
>
>if (exists(r4))
>{
>is.data.frame(get(r4))
>}
>else
>{
>a <- 0, b <- 0, c <- 0, d <- "x", r4 <- data.frame(cbind(a,b,c,d)) }
>
>Thanks for your help,
>B
>
> [[alternative HTML version deleted]]
>
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