On Jun 29, 2011, at 2:29 PM, Christopher T. Moore wrote:
Hello,
I have encountered some unexpected behavior in R that seems to occur
as a result of having the current year embedded in a number:
No. that is not the explanation.
########################################
#Some large numbers, representing IDs.
IDs <- c(41255689815201100, 41255699815201100, 41255709815201100)
41255689815201100 > 2*10^9
[1] TRUE
So you may think you are working with integers but youa re in fact
working with floating point numbers. See the R-FAQ
--
David.
#In scientific notation
IDs
[1] 4.125569e+16 4.125570e+16 4.125571e+16
#Change penalty.
options(scipen = 5)
#Why does R add 4?
IDs
[1] 41255689815201104 41255699815201104 41255709815201104
#Changing from numeric to character makes no difference.
as.character(IDs)
[1] "41255689815201104" "41255699815201104" "41255709815201104"
#What happens if I treat the numbers as characters?
IDs.character <- c("41255689815201100", "41255699815201100",
"41255709815201100")
#No change.
IDs.character
[1] "41255689815201100" "41255699815201100" "41255709815201100"
#R adds 4 upon converting to numeric.
as.numeric(IDs.character)
[1] 41255689815201104 41255699815201104 41255709815201104
#Is this problem occurring because the current year is embedded in
the number?
IDs <- c(41255689815201100, 41255699815201000, 41255709815201200)
#R is no longer adding 4 to the numbers without "2011".
IDs
[1] 41255689815201104 41255699815201000 41255709815201200
########################################
Am I doing something wrong? Any insight on how I can avoid the
problem of R changing numbers on its own? Are others able to
replicate this example? Is this some kind of bug? Am I right that
this problem is occurring because the current year is embedded in
the number? I discovered this when trying to merge two data sets,
one with IDs stored numbers and one with IDs as characters. I have
replicated this in Windows XP with R 2.12 and Windows 7 with R 2.13
(both 32- and 64-bit versions).
Thanks,
Chris
--
Christopher T. Moore, M.P.P.
Doctoral Student
Quantitative Methods in Education
University of Minnesota
44.9785°N, 93.2396°W
moor0...@umn.edu
http://umn.edu/~moor0554
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
