From sint@oeaw.ac.at  Thu May 10 22:31:59 2001
From: sint@oeaw.ac.at (sint@oeaw.ac.at)
Date: Thu, 10 May 2001 23:31:59 +0200 (MET DST)
Subject: [Rd] name creation with index arrays (PR#937)
Message-ID: <200105102131.XAA12164@pubhealth.ku.dk>

Full_Name: Peter Sint
Version: 1.22
OS: MacOS 9.04
Submission from: (NULL) (193.170.84.51)


The not so serious problem is probably not specific to Macintosh although I
found it there:

The small example from  R-intro works .
> x <- array(1:20,dim=c(4,5))
> i <- array(c(1:3,3:1),dim=c(3,2))
> i
  [,1] [,2]
[1,] 1 3
[2,] 2 2
[3,] 3 1
> x[i]
[1] 9 6 3

x[i] has no attribute!
> x
  [,1] [,2] [,3] [,4] [,5]
[1,] 1 5 9 13 17
[2,] 2 6 10 14 18
[3,] 3 7 11 15 19
[4,] 4 8 12 16 20
> x[i] <- 0
> x
  [,1] [,2] [,3] [,4] [,5]
[1,] 1 5 0 13 17
[2,] 2 0 10 14 18
[3,] 0 7 11 15 19
[4,] 4 8 12 16 20
>

>  colnames(x)<- c("c1","c2","c3","c4","c5")
> x[i]
[1] 9 6 3

BUT
> rownames(x)<- c("r1","r2","r3","r4")
> x[i]
NA NA r3 
 9  6  3 
> 
Rownames result in unsuccessful name formation (colnames do most likely not, but
this may depend on the order in the index array i). Better drop name making if
not o.k.

(Replacement [<- still works. 
Index matrices do not work on data frames, not a bug but a missing feature with
work around)
Reproduce:
x <- array(1:20,dim=c(4,5))
i <- array(c(1:3,3:1),dim=c(3,2))
i
x[i]
x
x[i] <- 0
x
colnames(x)<- c("c1","c2","c3","c4","c5")
x[i]
rownames(x)<- c("r1","r2","r3","r4")
x[i]

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[Rd] name creation with index arrays (PR#937)
sint@oeaw.ac.at