R help - Nov 2006 - how to check a R object's property

Hi,
I am writing a generic function and need to check if an arg is a data
frame or not. I could use
is.null(dim(x)) to get what i want. But i want to know if there is a
function which can tell me whether it is a list, a numeric vector, a
data frame, a factor and so on. Can R do that?

thanks.

-- 
Weiwei Shi, Ph.D
Research Scientist
GeneGO, Inc.

"Did you always know?"
"No, I did not. But I believed..."
---Matrix III

check class()

but if all you want is to test whether it's a data.frame or not:

is.data.frame()

b

On Nov 14, 2006, at 3:07 PM, Weiwei Shi wrote:
> Hi,
> I am writing a generic function and need to check if an arg is a data
> frame or not. I could use
> is.null(dim(x)) to get what i want. But i want to know if there is a
> function which can tell me whether it is a list, a numeric vector, a
> data frame, a factor and so on. Can R do that?
>
> thanks.
>
> --  
> Weiwei Shi, Ph.D
> Research Scientist
> GeneGO, Inc.
>
> "Did you always know?"
> "No, I did not. But I believed..."
> ---Matrix III
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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.

On Tue, 14 Nov 2006, Weiwei Shi wrote:
> Hi,
> I am writing a generic function and need to check if an arg is a data
> frame or not.
?is.data.frame
> I could use is.null(dim(x)) to get what i want.
In which case you would fail. Arrays and many other objects have non-NULL 
dims.
> But i want to know if there is a
> function which can tell me whether it is a list, a numeric vector, a
> data frame, a factor and so on. Can R do that?
Yes.  ?typeof, ?class, ?str, ?inherits ... and please do study 'An 
Introduction to R' (belatedly).

You do seem to be asking almost daily for people to read the documentation 
for you.  Please try

install.packages("fortunes"); library(fortunes);
fortune("WTFM")

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595