[R] rbind: inconsistent behaviour with empty data frames?

[David L Carlson]

What version of R are you using? 
I cannot replicate your results with R 2.15.2:

> df1 <- data.frame()
> df2 <- data.frame(foo=c(1, 2), bar=c("a", "b"))
> rbind(df1, df2)
  foo bar
1   1   a
2   2   b
> df1 <- data.frame(matrix(0, 0, 2))
> names(df1) <- names(df2)
> rbind(df1, df2)
  foo bar
1   1   a
2   2   b

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Dmitrii I.
> Sent: Wednesday, January 02, 2013 2:09 PM
> To: r-help at r-project.org
> Subject: [R] rbind: inconsistent behaviour with empty data frames?
> 
> The rbind on empty and nonempty data frames behaves inconsistently. I
> am
> not sure if by design.
> 
> In the first example, first row is deleted, which may or may not be on
> purpose:
> df1 <- data.frame()
> df2 <- data.frame(foo=c(1, 2), bar=c("a", "b"))
> rbind(df1, df2)
>     foo  bar
> 2   2     b
> 
> Now if we continue:
> df1 <- data.frame(matrix(0, 0, 2))
> names(df1) <- names(df2)
>     foo bar
> 2     1   a
> 3     2   b
> So now data frames combined successfully, but the row names have been
> increased by one.
> 
> Finally, if row names are strings, it works okay:
> row.names(df2) <- c("row1", "row2")
> rbind(df1, df2)
>           foo bar
> row1    1   a
> row2    2   b
> 
> Is this behaviour by design?
> 
> 	[[alternative HTML version deleted]]
> 
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