[R] Odp: if ( expr )

[Petr PIKAL]

Hi


r-help-bounces at r-project.org napsal dne 20.11.2007 10:03:53:

> 
> Hello,
> 
> I've searched the list but haven't found anything really applicable to 
my
> question. Any advice would be super.
> 
> I'm working on a snippet of R code and I have a function with a 
prototype
> like this:
> 
> foo <- function( x, ... ){
>      if( is.na(x)[1] ) {etc...}
> }
> 
> Where x is typically a vector of bools. 
> 
> At times, however, x can be NA, and yet at other super rare times x can 
be
> the result of this type of comparison:
> 
>  c(4,5,13,2,3,4,5,7) == numeric(0) 
> 
> which produces logical(0). When this is the case, if( is.na(x)[1] ) 
isn't
> happy. 

Check the length. In case of numeric(0) or logical(0) the length is 0 
which you can use for testing.

Regards
Petr

> 
> I'm trying to create a condition to my "if" statement inside foo that 
only
> is true when x is NA but that doesn't die when its a logical(0). 
> 
> Any suggestions on how best to approach this? 
> 
> As always, thanks a bunch,
> 
> Greg
> 
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