[R] Logical operator in R

[Rick Bilonick]

On 01/22/2016 10:46 AM, li li wrote:
> Hi all,
>    I encountered the following strange phenomenon.
> For some reason, the obs_p[1] and res1$st_p[89] have
> the same value but when I run "==", it returns FALSE.
> Can anyone help give some explanation on this?
>    Thanks very much!
>      Hanna
>
>> obs_p[1]
> [1] 0.002201438
>> res1$st_p[89]
> [1] 0.002201438
>> res1$st_p[89]==obs_p[1]
> [1] FALSE
>> res1$st_p[89]<obs_p[1]
> [1] FALSE
>> res1$st_p[89]>obs_p[1]
> [1] TRUE
>
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>
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I believe the decimal representation is only approximate. The real 
internal values in binary are different. If you want to have comparisons 
like this result in being considered equal, I think there is a way to 
use a fuzzy comparison but I don't remember the details.

Rick

-- 
Richard A. Bilonick, PhD
Assistant Professor
Dept. of Ophthalmology, School of Medicine
Dept. of Biostatistics, Graduate School of Public Health
Dept. of Orthodontics, School of Dental Medicine
University of Pittsburgh
Principal Investigator for the Pittsburgh Aerosol Research
  and Inhalation Epidemiology Study (PARIES)
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