Hi all,
If dimensions are added to a list, it will become a matrix-like hybrid
that calls itself a matrix, but returns lists for subset operations.
This was brought to my attention by a user that encountered such an
object and was quite confused by its behavior. Although I have not
found the code that created the object yet, I believe that code is
simply incorrect. Nevertheless, I wonder if R_data_class in attrib.c
should be a bit more discriminating and only return matrix or array
for atomic vectors. Perhaps something like this:
--- a/src/main/attrib.c
+++ b/src/main/attrib.c
@@ -536,7 +536,7 @@ SEXP R_data_class(SEXP obj, Rboolean singleString)
if(n == 0) {
SEXP dim = getAttrib(obj, R_DimSymbol);
int nd = length(dim);
- if(nd > 0) {
+ if(nd > 0 && isVectorAtomic(obj)) {
if(nd == 2)
klass = mkChar("matrix");
else
Here is an example that illustrates:
vv <- as.list(1:24)
dim(vv) <- c(6, 4)
vv
[,1] [,2] [,3] [,4]
[1,] 1 7 13 19
[2,] 2 8 14 20
[3,] 3 9 15 21
[4,] 4 10 16 22
[5,] 5 11 17 23
[6,] 6 12 18 24
class(vv)
[1] "matrix"
typeof(vv)
[1] "list"
vv[1, 1]
[[1]]
[1] 1
vv[1, ]
[[1]]
[1] 1
[[2]]
[1] 7
[[3]]
[1] 13
[[4]]
[1] 19
+ seth
--
Seth Falcon | Computational Biology | Fred Hutchinson Cancer Research Center
http://bioconductor.org
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
