R help - Nov 2007 - if ( expr )

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. 

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

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
> 
> ______________________________________________
> 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.

How about
if (is.na(c(x,1))[1]) .......

--- Gregory Wall <gdwall at ucdavis.edu> wrote:
> 
> 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. 
> 
> 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
> 
> ______________________________________________
> 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.
>