Comparisons of floating point numbers are problematic due to errors associated with the binary representation of decimal numbers. Computer scientists and programmers are aware of these problems (.e.g., Goldberg 1991) and yet people still use numerical methods which fail to account for floating point errors (this pitfall is the first to be highlighted in the First Circle of “The R Inferno” (Burns 2012)).
To avoid these and other numerical rounding issues, R’s help file for relational operators (e.g., ?'>'
) suggests using identical
and all.equal
when making numerical comparisons:
x1 < 0.5  0.3
x2 < 0.3  0.1
x1 == x2 # FALSE on most machines
identical(all.equal(x1, x2), TRUE) # TRUE everywhere
Inspired by R FAQ 7.31 and this Stack Overflow answer, this package provides new relational operators useful for performing floating point number comparisons with a set tolerance:
fpCompare ^{1}

base 

%>=% 
>= 
%>>% 
> 
%<=% 
<= 
%<<% 
< 
%==% 
== 
%!=% 
!= 
These functions use the base
relational operators to make comparisons, but incorporate a tolerance value (fpCompare.tolerance
) similar to all.equal
. The default fpCompare.tolerance
value is .Machine$double.eps^0.5
, set via options
. This is the same default used in all.equal
for numeric comparisons.
install.packages("fpCompare")
library(devtools)
install_github("PredictiveEcology/fpCompare")
Burns, Patrick. 2012. The R Inferno. 2nd ed. http://www.burnsstat.com/pages/Tutor/R_inferno.pdf.
Goldberg, David. 1991. “What every computer scientist should know about floatingpoint arithmetic.” ACM Computing Surveys, 171–264. http://dl.acm.org/citation.cfm?id=103163.