Prof Brian D Ripley <ripley at stats.ox.ac.uk> writes:
On Wed, 31 May 2000, Denis White wrote:
In Splus this works,
a <- data.frame(matrix(round(runif(10),0),nrow=2,ncol=5))
a[a == 1] <- 2
but in R only if a is matrix,
a[a == 1] <- 2
Error in [<-.data.frame(*tmp*, a == 1, value = 2) :
matrix subscripts not allowed in replacement
Was this a design decision? Sorry if I missed it in
An Introduction to R.
S-PLUS differs from the original S here, as I understand it.
So it was an S-PLUS design decision as I understand it. S-PLUS says:
else if(nargs() == 3) {
# really ambiguous, but follow common use as if list,
# except when one subscript is a logical matrix the shape of x, then treat
# as if x were a matrix.
Semantically it is a rather strange thing to do since elements
in different columns of a data matrix can be of different type.
And some really weird stuff *does* happen in Splus 3.4:
Warning messages:
replacement values not all in levels(x): NA's generated in:
"[<-.factor"(.A0,
i[, k, drop = T], value = .A1)
a
a b c
1 1 1 1
2 2 2 2
3 3 3 3
4 4 4 4
5 x NA x
6 6 6 6
7 7 7 7
8 8 8 8
9 9 9 9
10 10 10 10
a[a==4]<-"y"
Warning messages:
1: Data length is not an even multiple of group length in:
split(Value,
factor(col(i)[i], levels = seq(len = ncol(i))))
2: replacement values not all in levels(x): NA's generated in:
"[<-.factor"(.\
A0, i[, k, drop = T], value = .A1)
3: replacement values not all in levels(x): NA's generated in:
"[<-.factor"(.\
A0, i[, k, drop = T], value = .A1)
a
a b c
1 1 1 1
2 2 2 2
3 3 3 3
4 NA NA 4
5 x NA x
6 6 6 6
7 7 7 7
8 8 8 8
9 9 9 9
10 10 10 10
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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