Hi all,
I am working on an application in which we'd like to use attributes to
attach simple metadata to arbitrary R objects. It is essential that all
functions that will work on the original object will also work on the
object after metadata attributes have been added. However, this is not
always the case for vectors: functions such as barplot, diffinv, and rle
use is.vector, which (as documented and as discussed previously on this
list) returns FALSE for a vector that has any attributes other than
"names". For example,
> x <- 1:3
> attr(x, "date") <- date()
> barplot(x)
Error in barplot.default(x) : 'height' must be a vector or a matrix
It strikes me that is.vector may be an overly strict test in these
cases. Shouldn't barplot(x) behave the same regardless of whether vector
x has any (non-special) attributes? In barplot.default, what if
is.vector(x) were replaced with something along the lines of:
is.atomic(x) && is.null(dim(x))
Admittedly, other functions currently using is.vector may require
something slightly different. One such example is data.frame, which uses
is.vector when applying recycling rules. It appears it is used at least
in part to filter out AsIs objects, so a specific test of whether the
object class is AsIs may be appropriate?
No doubt a slew of functions in user-contributed packages use is.vector
in similar fashion, so even modifying core functions wouldn't fully
solve our particular problem. On that note, I don't suppose there's hope
of revisiting the definition of is.vector itself? Bear in mind, I do
appreciate that there are good reasons for its current behavior, and
compatibility constraints on changing it.
Thanks,
Jim
------------------------------
James Regetz, Ph.D.
Scientific Programmer/Analyst
National Center for Ecological Analysis & Synthesis
735 State St, Suite 300
Santa Barbara, CA 93101
