Yes, I'm also strongly in favor of having an option for this. If
there was an option in base R for controlling this we would just use
that and get rid of the separate RProtoBuf.int64AsString option we use
in the RProtoBuf package on CRAN to control whether 64-bit int types
from C++ are returned to R as numerics or character vectors.
I agree that reasonable people can disagree about the default, but I
found my original bug report about this, so I will counter Robert's
example with my favorite example of what was wrong with the previous
behavior :
tmp<-data.frame(n=c("72057594037927936", "72057594037927937"),
name=c("foo", "bar"))
length(unique(tmp$n))
# 2
write.csv(tmp, "/tmp/foo.csv", quote=FALSE, row.names=FALSE)
data <- read.csv("/tmp/foo.csv")
length(unique(data$n))
# 1
- Murray
On Sat, Apr 19, 2014 at 10:06 AM, Simon Urbanek
<simon.urba...@r-project.org> wrote:
On Apr 19, 2014, at 9:00 AM, Martin Maechler <maech...@stat.math.ethz.ch>
wrote:
McGehee, Robert <robert.mcge...@geodecapital.com>
on Thu, 17 Apr 2014 19:15:47 -0400 writes:
This is all application specific and
sort of beyond the scope of type.convert(), which now behaves as it
has been documented to behave.
That's only a true statement because the documentation was changed to
reflect the new behavior! The new feature in type.convert certainly does
not behave according to the documentation as of R 3.0.3. Here's a snippit:
The first type that can accept all the
non-missing values is chosen (numeric and complex return values
will represented approximately, of course).
The key phrase is in parentheses, which reminds the user to expect a
possible loss of precision. That important parenthetical was removed from
the documentation in R 3.1.0 (among other changes).
Putting aside the fact that this introduces a large amount of
unnecessary work rewriting SQL / data import code, SQL packages, my biggest
conceptual problem is that I can no longer rely on a particular function
call returning a particular class. In my example querying stock prices,
about 5% of prices came back as factors and the remaining 95% as numeric,
so we had random errors popping in throughout the morning.
Here's a short example showing us how the new behavior can be
unreliable. I pass a character representation of a uniformly distributed
random variable to type.convert. 90% of the time it is converted to
"numeric" and 10% it is a "factor" (in R 3.1.0). In the 10% of cases in
which type.convert converts to a factor the leading non-zero digit is
always a 9. So if you were expecting a numeric value, then 1 in 10 times
you may have a bug in your code that didn't exist before.
options(digits=16)
cl <- NULL; for (i in 1:10000) cl[i] <-
class(type.convert(format(runif(1))))
table(cl)
cl
factor numeric
990 9010
Yes.
Murray's point is valid, too.
But in my view, with the reasoning we have seen here,
*and* with the well known software design principle of
"least surprise" in mind,
I also do think that the default for type.convert() should be what
it has been for > 10 years now.
I think there should be two separate discussions:
a) have an option (argument to type.convert and possibly read.table) to
enable/disable this behavior. I'm strongly in favor of this.
b) decide what the default for a) will be. I have no strong opinion, I
can see arguments in both directions
But most importantly I think a) is better than the status quo - even if
the discussion about b) drags out.
Cheers,
Simon
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