Converting units in R

Question

I would like to convert from imperial units to metric and vice versa in R. How do I go about doing that?

If there is no current way of doing that, how can I create a package that would?

Answer 1

Edit: There is now an encyclopedic units package: NISTunits

The nature of the units may affect the presence or absence. In general I think, unfortunately, that @gsk3 is correct. There are some function in the 'Hmisc', 'gdata', and 'marelac' packages:

Setting a units attribute (for more than just time objects): http://finzi.psych.upenn.edu/R/library/Hmisc/html/units.html

Medical: http://finzi.psych.upenn.edu/R/library/gdata/html/ConvertMedUnits.html

'marelac' Index (mostly specialized to oceanography) http://finzi.psych.upenn.edu/R/library/marelac/html/00Index.html

Temperature: http://finzi.psych.upenn.edu/R/library/marelac/html/convert_T.html

Barometric: http://finzi.psych.upenn.edu/R/library/marelac/html/convert_p.html

Package "dielectric" was mentioned by @Brian Diggs in an answer to a similar question: Link to 'constants' help page in package 'dielectric'

I think those will provide examples of doing so and the function package.skeleton should help with the mechanics of package creation. I think the package would be a welcome addition.

Update: The 'udunits2' package was mentioned by Gabor Grothendieck in a similar question to rhelp July 23, 2012. It appears to require installation of a stand-alone OS-specific package of the same name. Without such installation you get a rather unhelpful error message:

> ud.convert(1, "miles", "km")  
Error in ud.convert(x, "miles", "km") : 
  Units miles and km are not convertible

Answer 2

I know this is very late, but the package measurements has a function conv_unit() that may be what you're looking for. You enter the imperial value you have, what unit you're converting from (e.g. 'ft') and what you want to convert to (e.g. 'km'). It has a variety of different dimensions (not just length).