Creating edges (rows) for several mentions in one tweet, problems

Question

In Dave´s answer to 'Creating edges (rows) for several mentions in one tweet' running the folliwing Script:

plyr::ddply(tweets, c("text"), function(x){
mention <- unlist(stringr::str_extract_all(x$text, "@\\w+"))
# some tweets do not contain mentions, making this necessary:
if (length(mention) > 0){
    return(data.frame(mention = mention))
} else {
    return(data.frame(mention = NA))    
}}) 

I have a problem for some tweets list. I got the error:

Error in if (empty(.data)) return(.data) : 
  missing value where TRUE/FALSE needed.

Thanks for help.

Answer 1

Compare these two results:

if(NA > NA) 'yes' else 'no'
#Error in if (NA > NA) "yes" else "no" : 
#  missing value where TRUE/FALSE needed

if(NA > NA && !is.na(NA > NA)) 'yes' else 'no'
#[1] "no"

The first expression is returning the same error message that you received for similar reasons. The conditional test is expecting a TRUE or FALSE in order to move on. My test NA > NA does not have a truth value so NA is returned. Therefore in the second test I included an extra check to ignore NA conditional results.