[R] Check the class of an object

David Winsemius dwinsemius at comcast.net
Tue Jul 23 18:15:32 CEST 2013

On Jul 23, 2013, at 5:36 AM, Simon Zehnder wrote:

> Dear R-Users and R-Devels,
> I have large project based on S4 classes. While writing my unit tests I found out, that 'is' cannot test for a specific class, as also inherited classes can be treated as their super classes. I need to do checks for specific classes. What I do right now is sth. like
> if (class(myClass) == "firstClass") {

I would think that you would need to use `%in%` instead. 

 if( "firstClass" %in% class(myObject) ){

 Objects can have more than one class, so testing with "==" would fail in those instances.

> } else if (class(myClass) == "secondClass") {
> }
> Is this the usual way how classes are checked in R?

Well, `inherits` IS the usual way.

> I was expecting some specific method (and 'inherits' or 'extends' is not what I look for)...
> Best
> Simon
> 	[[alternative HTML version deleted]]

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David Winsemius
Alameda, CA, USA

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