?all.equal
--
Clint Bowman INTERNET: cl...@ecy.wa.gov
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On Tue, 23 Aug 2011, Daniel Lai wrote:
Greetings all,
I'm porting an algorithm from MATLAB to R, and noticed some minor
discrepancies in small decimal values using rowSums and colSums which are
exacerbated after heavy iteration and log space transformation. This was
rather perplexing as both programs claimed and appeared to use the IEEE 754
standard for floating point arithmetic (confirmed with manual basic
operations). After some tracing and testing, I've managed to isolated a
minimal working example as follows:
a = 0.812672
b = 0.916541
c = 0.797810
sum(c(a, b, c)) == (a + b + c)
[1] FALSE
Should I attribute this to the woes of working with floating point numbers
and accept it? i.e.
sprintf("%.30f", sum(c(a, b, c)))
[1] "2.527022999999999797182681504637"
sprintf("%.30f", (a + b + c))
[1] "2.527023000000000241271891354700"
Change the OS or version I'm using?
MAC OSX 10.5.8:
sessionInfo()
R version 2.13.1 (2011-07-08)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)
attached base packages:
[1] stats graphics grDevices utils datasets methods base
Linux 2.6.34:
R version 2.12.0 (2010-10-15)
Platform: x86_64-unknown-linux-gnu (64-bit)
attached base packages:
[1] stats graphics grDevices utils datasets methods base
Or report this as a bug?
Thanks,
Daniel
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and provide commented, minimal, self-contained, reproducible code.
