[R] Significant digits for checking values of variable?

[jim holtman]

FAQ 7.31

On Wed, Aug 27, 2008 at 11:51 AM, David Afshartous
<dafshartous at med.miami.edu> wrote:
>
> All,
>
> I'm witnessing some strange behavior when checking the values of one of my
> variables.  My guess is that it has something to do with the number of
> significant digits being represented, but perhaps not as my variable was
> created from other variables that only had one decimal place.  See below.
> I'm sure this is something basic, any suggestions much appreciated.
>
> Cheers,
> David
>
>
>> visit.2.SEK.delta.baseline
>  [1]  0.1 -0.7  0.8 -0.1 -0.5  0.8  0.7  0.2  0.4  0.3  0.6  0.6  0.3  0.8
> 0.8  0.3  0.4  0.8
>> visit.2.SEK.delta.baseline > 0
>  [1]  TRUE FALSE  TRUE FALSE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE
> TRUE  TRUE  TRUE  TRUE  TRUE  TRUE
>> visit.2.SEK.delta.baseline ==  .8
>  [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
> FALSE FALSE FALSE FALSE FALSE FALSE
> ### but some of the values are equal to .8
>
> ## here it is okay when I try to reproduce
>>  junk = c(0.1, -0.7,0.8, -0.1, -0.5,  0.8,  0.7,  0.2,  0.4,  0.3,  0.6,  0.6,
> 0.3,  0.8,  0.8,  0.3,  0.4,  0.8 )
>> junk == .8
>  [1] FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE FALSE FALSE
> FALSE  TRUE  TRUE FALSE FALSE  TRUE
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?