Using ifelse with write.table

Question

I'm writing a file using ifelse:

ifelse("out.csv" %in% list.files(),
       write.table(summary, "out.csv", sep=",", col.names=FALSE, row.names=FALSE, append=TRUE),
       write.table(summary, "out.csv", sep=",", row.names=FALSE)
)

It seems to work fine but throws up an error: replacement has length zero

Any risk to using this code or a better way to do things?

Thanks

Answer 1

As noted in the help, ifelse evaluates both the true and false arguments regardless of the value of the condition. What you want is a plain if .

if("out.csv" %in% list.files()) {
   write.table(summary, "out.csv", sep=",", row.names=FALSE,
       col.names=FALSE, append=TRUE)
} else {
   write.table(summary, "out.csv", sep=",", row.names=FALSE)
}