[Rd] as.data.frame: Error in "names<-.default" (PR#7808)

[Robert.McGehee at geodecapital.com]

Hello,
I found a potential problem in R 2.1.0 (and R 2.0.1)

I expect that

> tmp <- FUN(x1, x2, x3, x4)
> as.data.frame(tmp)

is the same as
> as.data.frame(FUN(x1, x2, x3, x4))

since the tmp variable in this case is unnecessary.

However, below I will demonstrate that under an odd set of conditions, I
can correctly perform as.data.frame(tmp), but not as.data.frame(FUN(x1,
x2, x3, x4)). 

## This code works correctly
FUN <- function(x1, x2, x3, x4) 
     cbind(x1[, 1, 1:2], x1[, 2, 1:2])[, 1]

x1 <- array(1:9, c(3, 3, 3))
tmp <- FUN(x1[1:3, , ], x2 = c("a", "b"), x3 = c("a", "b"), x4 = c("a",
"b"))

## Works correctly
as.data.frame(tmp)  

  tmp
1   1
2   2
3   3


## This (supposedly equivalent) code gives an error

as.data.frame(FUN(x1[1:3,,], x2 = c("a", "b"), x3 = c("a", "b"), x4 =
c("a", "b")))

Error in "names<-.default"(`*tmp*`, value = c("FUN(x1[1:3, , ], x2 =
c(\"a\", \"b\"), x3 = c(\"a\", \"b\"), x4 = c(\"a\", ",  : 
	'names' attribute [2] must be the same length as the vector [1]

Note, that while the extra (unused) arguments in FUN seem unnecessary,
as well as the odd indexing, the problem disappears when I remove the
extraneous values. Unfortunately, I have not found a more elegant way to
present this problem, but hopefully this code will be helpful.

Robert

Robert McGehee
Geode Capital Management, LLC
53 State Street, 5th Floor | Boston, MA | 02109
Tel: 617/392-8396    Fax:617/476-6389
mailto:robert.mcgehee at geodecapital.com



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