How to include NA in ifelse?

Question

I am trying to create a column ID based on logical statements for values of other columns. For example, in the following dataframe

test <- st         


        

Answer 1

So, I hear this works:

Data$X1<-as.character(Data$X1)
Data$GEOID<-as.character(Data$BLKIDFP00)
Data<-within(Data,X1<-ifelse(is.na(Data$X1),GEOID,Data$X2)) 

But I admit I have only intermittent luck with it.