# [Rd] row names and identical

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Sat, 14 Jul 2007 16:11:10 -0400

Below x1, x2 and x3 all have the same data and all have the same value for row.names(x); however, the internal values of their row.names differ. The internal value of row.names is c(NA, -4L) for x1, c(NA, 4L) for x2 and c("1", "2", "3", "4") for x3; nevertheless, identical regards x1 and x2 as identical while x3 is not identical to either of x1 or x2.

Is this intended?
Desirable?
Why do we need different internal representations for row.names for x1 and x2?

> x1 <- x2 <- x3 <- data.frame(x = 11:14)
> row.names(x2) <- 1:4
> row.names(x3) <- as.character(1:4)
>
> # they all have the same value for row.names()
> row.names(x1)

[1] "1" "2" "3" "4"
> row.names(x2)

[1] "1" "2" "3" "4"
> row.names(x3)

[1] "1" "2" "3" "4"
>
> # but internally they are all different
> dput(x1)

structure(list(x = 11:14), .Names = "x", row.names = c(NA, -4L ), class = "data.frame")
> dput(x2)

structure(list(x = 11:14), .Names = "x", row.names = c(NA, 4L ), class = "data.frame")
> dput(x3)

structure(list(x = 11:14), .Names = "x", row.names = c("1", "2", "3", "4"), class = "data.frame")
>
> # identical regards x1 and x2 as the same while x3 differs
> identical(x1, x2)

[1] TRUE
> identical(x1, x3)

[1] FALSE
> identical(x2, x3)

[1] FALSE
>
> R.version.string # XP
[1] "R version 2.5.1 (2007-06-27)"

R-devel_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel Received on Sat 14 Jul 2007 - 20:13:45 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Mon 16 Jul 2007 - 03:36:48 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-devel. Please read the posting guide before posting to the list.