https://github.com/predictiveecology/fpcompare

Reliable comparison of floating point numbers in R
https://github.com/predictiveecology/fpcompare

r-package

Last synced: over 1 year ago
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Reliable comparison of floating point numbers in R

• Host: GitHub
• URL: https://github.com/predictiveecology/fpcompare
• Owner: PredictiveEcology
• License: gpl-3.0
• Created: 2015-04-02T20:15:04.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2024-11-25T22:57:05.000Z (over 1 year ago)
• Last Synced: 2024-11-25T23:31:58.321Z (over 1 year ago)
• Topics: r-package
• Language: R
• Homepage: http://fpcompare.predictiveecology.org
• Size: 214 KB
• Stars: 6
• Watchers: 5
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • Changelog: NEWS.md
  • License: LICENSE

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README

          
# fpCompare

[![R build status](https://github.com/PredictiveEcology/fpCompare/workflows/R-CMD-check/badge.svg)](https://github.com/PredictiveEcology/fpCompare/actions)

[![CRAN_Status_Badge](http://www.r-pkg.org/badges/version/fpCompare)](https://CRAN.R-project.org/package=fpCompare)

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[![Codecov test coverage](https://codecov.io/gh/PredictiveEcology/fpCompare/branch/master/graph/badge.svg)](https://app.codecov.io/gh/PredictiveEcology/fpCompare?branch=master)

## Reliable comparison of floating point numbers

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 and yet people still use numerical methods which fail to account for floating point errors (this pitfall is the first to be highlighted in Circle 1 of Burns (2012) [The R Inferno](https://www.burns-stat.com/pages/Tutor/R_inferno.pdf)).

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:

```r

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](https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f) and [this Stack Overflow answer](https://stackoverflow.com/a/2769618/1380598), 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.

```r

# set telorance value

tol = .Machine$double.eps^0.5       # default value

options(fpCompare.tolerance = tol)

# perform comparisons

x1 <- 0.5 - 0.3

x2 <- 0.3 - 0.1

x1 == x2         # FALSE on most machines

x1 %==% x2       # TRUE everywhere

```

[^1]: The `%<<%` and `%>>%` symbols are used instead of `%<%` and `%>%` to avoid a conflict with `magrittr`'s pipe operator (`%>%`).

# Installation

## From CRAN

```r

install.packages("fpCompare")

```

## From GitHub

```r

library(devtools)

install_github("PredictiveEcology/fpCompare")

```

# Bug Reports

[https://github.com/PredictiveEcology/fpCompare/issues](https://github.com/PredictiveEcology/fpCompare/issues)