r - Collapse a data.frame into a vector

Question

I have a data frame like this:

COL1  COL2  COL3 

   a           h
   b     f    
   c     g       
   d           j

I would like the following output:

 COL  
   a    
   b    
   c    
   d   
   f   
   g   
   h   
   j   

How this can be done? Thanks in advance!

Answer 1

If your data.frame is named dat, try:

unlist(dat, use.names=FALSE)

You may also want to try the following:

as.character(unlist(dat, use.names=FALSE))
c(na.omit(as.character(unlist(dat, use.names=FALSE))))

which might be useful if your data are entered as factors.

Also, in your question, you make it appear that you don't actually have a basic "vector", but rather a one-column data.frame. Thus, something like dat2 <- data.frame(COL = c(na.omit(as.character(unlist(dat, use.names=FALSE))))) might be what you're looking for.