ISNA(NA_REAL) == false?
On 1/17/2007 7:05 AM, David Faden wrote:
Hi, Is it expected that ISNA(NA_REAL) will evaluate to false?
No, but what it does is compare to something in memory. If R hasn't initialized, that location won't be set, and you'll get wrong results. See the "Using these functions in your own C code" for instructions on how to build things for your sort of use. Your code was linked as though it would be called from a running version of R, which had handled the initialization. Duncan Murdoch From Writing
R Extensions, I'd expected it instead to evaluate to true, but this
seems not to be the case. What value should one use to represent an NA
in native code if not NA_REAL? (I am trying to test some code by using
a small C++ application to call it. Ultimately the code will be called
from within R, but I'm hoping to get more information out of gdb this
way. To get this to work, though, I need to be able to get the
equivalent of expressions such as rep(c(NA, 1), 50), in my native
code.)
isnan, etc., seem to be available.
Below is some example code and its output on my computer, along with
some version info. Thanks much for any insights into what's going on.
David
----
dfaden at iastate.edu
AIM: pitulx
----
na.cpp:
#include <iostream>
#include <R_ext/Arith.h>
int main()
{
if (!ISNA(NA_REAL)) {
std::cout << "Hm.\n";
}
}
Output:
$ g++ -I/Library/Frameworks/R.framework/Versions/Current/Resources/include
-L/Library/Frameworks/R.framework/Versions/Current/Resources/lib -lR
na.cpp
$ R CMD ./a.out
Hm.
----
g++ version:
i686-apple-darwin8-g++-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5250)
R version:
platform i386-apple-darwin8.8.1
arch i386
os darwin8.8.1
system i386, darwin8.8.1
status
major 2
minor 4.1
year 2006
month 12
day 18
svn rev 40228
language R
version.string R version 2.4.1 (2006-12-18)
I'm running Mac OS X 10.4.8.
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