[R] if/else help

[MacQueen, Don]

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-bounces at r-project.org on behalf of bcrombie at 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]]
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>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.