[R] which() function not finding certain numbers

[Jeff Newmiller]

FAQ 7.31
?is.equal
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Sent from my phone. Please excuse my brevity.

Tom Bird <tomasbird at gmail.com> wrote:

>Hi,
>
>I am using 32-bit R v 2.15.1, on Mac OsX v 10.6.8 with R GUI 1.52
>Leopard
>build 32-bit (6188).  I have also replicated this error on R 2.13.2 on
>a
>windows 7 machine.
>
>In some sequences of numbers,  I am unable to use the which() function
>to
>index certain values.    It seems to be primarily numbers with a 3 in
>the
>decimal.
>For example:
>
>> S=seq(0,4,0.01)
>
>> which(S==2.02)
>
>[1] 203
>
>> which(S==2.03)
>
>integer(0)
>
>> which(S==2.04)
>
>[1] 205
>
>> which(S==2.04)
>
>[1] 205
>
>> which(S==3.03)
>
>integer(0)
>
>> which(S==3.3)
>
>integer(0)
>
>> which(S==3.)
>
>[1] 301
>
>> which(S==3.5)
>
>[1] 351
>
>>
>
>I'm not even sure if this is a bug,  or just some misunderstanding of
>the
>seq() or which() functions,  but any thoughts would be appreciated.
>
>TB
>
>	[[alternative HTML version deleted]]
>
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