R: losing column names when adding rows to an empty data frame

Question

I am just starting with R and encountered a strange behaviour: when inserting the first row in an empty data frame, the original column names get lost.

example:

Answer 1

Instead of constructing the data.frame with numeric(0) I use as.numeric(0).

a<-data.frame(one=as.numeric(0), two=as.numeric(0))

This creates an extra initial row

a
#    one two
#1   0   0

Bind the additional rows

a<-rbind(a,c(5,6))
a
#    one two
#1   0   0
#2   5   6

Then use negative indexing to remove the first (bogus) row

a<-a[-1,]
a

#    one two
#2   5   6

Note: it messes up the index (far left). I haven't figured out how to prevent that (anyone else?), but most of the time it probably doesn't matter.