abline is a not an S3 generic and can be used better. about faster HOT 3 CLOSED

Thanks for the valuable comments! Most are spot on, and I will correct the problems. I do differ with you on two points. First, AFAIK no one considers an R factor to be an S3 object. Second, regarding the 'mtcars' dataset, the name alludes to the fact that the data comes from Motor Trend, a popular American car magazine in the 1960s/70s; the weights are almost certainly in pounds, just like the gas mileage is in miles/gallon rather than say km/liter.

from faster.

Addressing your points:

1. In my experience, people do consider factors to be S3 objects. This is exactly why a lot of R tutorials warn about how they sometimes act like integers and sometimes act like characters. A well-known example is section 8.2. of the R Inferno. The documentation for factors also contains many such warnings. Regardless, whether or not factors are S3 objects is not a matter of opinion. Run methods(class=factor) and you will see many generic functions that dispatch to them.
2. According to ??datasets::mtcars, the wt variable is "Weight (1000 lbs)". I think we're both right here. Yes, they're pounds, but the reader ought to be told that adding 100 pounds means adding 0.1.

from faster.

R factors can be both very powerful and highly annoying. In my 'regtools' package (here on GitHub), I actually have 5 or 6 utilities to deal with problems arising with factors. But I've never heard anyone consider factors to be S3. I've been active in R since almost the beginning (and was an S user before R), have served in editorial capacity with 2 R-related journals etc.

from faster.