K.H. Kim has an article on unit conversion in R:
Data
mtcarshas a column namedmpg.mpgmeans miles per gallon. ‘Mile’ and ‘gallon’ are units for length and volume. A mile is approximately 1.6 kilometers and a gallon is approximately 3.7 liters. Mile and gallon sound unfamiliar to people who live outside England or U.S.A. because international standard units for length and volume are meter and liter.In this post, we will learn how to convert a unit to another unit, for instance, we will convert mpg to km/L, which is more comprehensible to people who use SI units
This is something that I’m surprised languages don’t do more of. F# has the concept of units of measure but these are compile-time—at runtime, you can still break the rules. And in most languages, type systems are so simplistic that it’s all just plain decimal math. H/T R-bloggers.