On 13-04-30 3:38 AM, Suharto Anggono Suharto Anggono wrote:
This is just info.
I recently got something like this.
x <- factor(c("A","A","B","B"), levels=c("A","B"))
y <- factor(c("a","b","a","b"), levels=c("a","b"))
table(x, y)[, "a"] / table(x)
x
A B
0.5 0.5
attr(,"class")
[1] "table"
The printing indicates that the result is of class 'table'. But, the 'print' method of
class 'table' does not print attr(,"class"). It seems that 'print.default' is
used in the printing. I am OK with it, just unusual.
I think, that is another symptom of an already known behavior as in the
following:
- PR#2345: difftime arithmetic
- PR#13209: S4 object does not commute?
There are no S4 objects or time objects involved here, so it's likely
something different.
I notice the following strange behaviour. If I save the ratio in a
variable, it prints differently with an explicit print than with auto
printing:
x <- factor(c("A","A","B","B"), levels=c("A","B"))
y <- factor(c("a","b","a","b"), levels=c("a","b"))
ratio <- table(x, y)[, "a"] / table(x)
ratio # shows what you saw
print(ratio) # shows what you expected
Something else that's a little strange: the numerator does not have
class "table", so you can get the same results with
ratio <- c(1,1) / table(x)
Looking at the internals, I see that the ratio variable has a class
attribute, but does not have its "object bit" set.
So it looks like the bug is in the implementation of "/". Either it
should drop the class, or it should set the object bit.
The difference in printing between auto-printing and explicit printing
may be worth addressing, but really objects like ratio shouldn't exist,
so it's not surprising that they behave strangely.
Duncan Murdoch
sessionInfo()
R version 3.0.0 (2013-04-03)
Platform: i386-w64-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
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