I am dealing with an object that sometimes has a certain
attribute, sometimes doesn't. How do I check for this?
"exists" doesn't work...
====================== > z=c()
> z$a = c("c", "d", "f")
> z
$a
[1] "c" "d" "f"
> exists("z")
[1] TRUE
> exists("z$a")
[1] FALSE
======================
...basically, I want something that returns TRUE if the $a
exists in z...
Thanks!
Nick
--
===================================================Nicholas J. Matzke
Ph.D. Candidate, Graduate Student Researcher
Huelsenbeck Lab
Center for Theoretical Evolutionary Genomics
4151 VLSB (Valley Life Sciences Building)
Department of Integrative Biology
University of California, Berkeley
Graduate Student Instructor, IB200B
Principles of Phylogenetics: Ecology and Evolution
http://ib.berkeley.edu/courses/ib200b/
http://phylo.wikidot.com/
Lab websites:
http://ib.berkeley.edu/people/lab_detail.php?lab=54
http://fisher.berkeley.edu/cteg/hlab.html
Dept. personal page:
http://ib.berkeley.edu/people/students/person_detail.php?person=370
Lab personal page:
http://fisher.berkeley.edu/cteg/members/matzke.html
Lab phone: 510-643-6299
Dept. fax: 510-643-6264
Cell phone: 510-301-0179
Email: matzke at berkeley.edu
Mailing address:
Department of Integrative Biology
3060 VLSB #3140
Berkeley, CA 94720-3140
-----------------------------------------------------
"[W]hen people thought the earth was flat, they were wrong.
When people thought the earth was spherical, they were
wrong. But if you think that thinking the earth is spherical
is just as wrong as thinking the earth is flat, then your
view is wronger than both of them put together."
Isaac Asimov (1989). "The Relativity of Wrong." The
Skeptical Inquirer, 14(1), 35-44. Fall 1989.
http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
Oh wait, this basically does it:
> if ("a" %in% attributes(z)$names)
+ print(TRUE)
[1] TRUE
(but there may be a better way)
Cheers!
Nick
On 2/2/11 7:20 PM, Nick Matzke wrote:> I am dealing with an object that sometimes has a certain
> attribute, sometimes doesn't. How do I check for this?
> "exists" doesn't work...
>
> ======================> > z=c()
> > z$a = c("c", "d", "f")
> > z
> $a
> [1] "c" "d" "f"
>
> > exists("z")
> [1] TRUE
>
> > exists("z$a")
> [1] FALSE
> ======================>
> ...basically, I want something that returns TRUE if the $a
> exists in z...
>
> Thanks!
> Nick
>
>
>
--
===================================================Nicholas J. Matzke
Ph.D. Candidate, Graduate Student Researcher
Huelsenbeck Lab
Center for Theoretical Evolutionary Genomics
4151 VLSB (Valley Life Sciences Building)
Department of Integrative Biology
University of California, Berkeley
Graduate Student Instructor, IB200B
Principles of Phylogenetics: Ecology and Evolution
http://ib.berkeley.edu/courses/ib200b/
http://phylo.wikidot.com/
Lab websites:
http://ib.berkeley.edu/people/lab_detail.php?lab=54
http://fisher.berkeley.edu/cteg/hlab.html
Dept. personal page:
http://ib.berkeley.edu/people/students/person_detail.php?person=370
Lab personal page:
http://fisher.berkeley.edu/cteg/members/matzke.html
Lab phone: 510-643-6299
Dept. fax: 510-643-6264
Cell phone: 510-301-0179
Email: matzke at berkeley.edu
Mailing address:
Department of Integrative Biology
3060 VLSB #3140
Berkeley, CA 94720-3140
-----------------------------------------------------
"[W]hen people thought the earth was flat, they were wrong.
When people thought the earth was spherical, they were
wrong. But if you think that thinking the earth is spherical
is just as wrong as thinking the earth is flat, then your
view is wronger than both of them put together."
Isaac Asimov (1989). "The Relativity of Wrong." The
Skeptical Inquirer, 14(1), 35-44. Fall 1989.
http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
On Wed, Feb 2, 2011 at 7:22 PM, Nick Matzke <matzke at berkeley.edu> wrote:> Oh wait, this basically does it: > >> if ("a" %in% attributes(z)$names) > + print(TRUE) > [1] TRUE > > (but there may be a better way)If z is a list, you can test is.null(z$a) Peter
On Wed, Feb 2, 2011 at 7:25 PM, Peter Langfelder <peter.langfelder at gmail.com> wrote:> On Wed, Feb 2, 2011 at 7:22 PM, Nick Matzke <matzke at berkeley.edu> wrote: >> Oh wait, this basically does it: >> >>> if ("a" %in% attributes(z)$names) >> + print(TRUE) >> [1] TRUE >> >> (but there may be a better way) > > If z is a list, you can test > > is.null(z$a)Nope, e.g.> z <- list(a=NULL) > str(z)List of 1 $ a: NULL Instead, test by:> is.element("a", names(z))[1] TRUE or equivalently> ("a" %in% names(z))[1] TRUE or> any(names(z) == "a")[1] TRUE My $.02 /Henrik> > Peter > > ______________________________________________ > 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. >