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

One way to make this work generically and with the least amount of re-typing the column names is the following. This method doesn't require hacking the NA or 0.

rs <- data.frame(i=numeric(), square=numeric(), cube=numeric())
for (i in 1:4) {
    calc <- c(i, i^2, i^3)
    # append calc to rs
    names(calc) <- names(rs)
    rs <- rbind(rs, as.list(calc))
}

rs will have the correct names

> rs
    i square cube
1   1      1    1
2   2      4    8
3   3      9   27
4   4     16   64
> 

Another way to do this more cleanly is to use data.table:

> df <- data.frame(a=numeric(0), b=numeric(0))
> rbind(df, list(1,2)) # column names are messed up
>   X1 X2
> 1  1  2

> df <- data.table(a=numeric(0), b=numeric(0))
> rbind(df, list(1,2)) # column names are preserved
   a b
1: 1 2

Notice that a data.table is also a data.frame.

> class(df)
"data.table" "data.frame"