[R] A behaviour pattern that I find mysterious.

[Rolf Turner]

Consider the following:

x <- letters[1:5]
x < 0

This gives

> [1] FALSE FALSE FALSE FALSE FALSE

which kind of makes sense, I guess, though I would a priori have 
expected all NAs.

But then do:

x[3] <- "*"
x < 0

This gives

> [1] FALSE FALSE  TRUE FALSE FALSE

which puzzles me.  Why is "*" considered to be less than 0?

At one point I made the conjecture that it had something to do with the 
ordering of ASCII characters, but it does not seem to.  A little more 
investigation led me to conjecture that all ASCII characters except 
real-live letters and numerals come out as being less than 0.

Can anyone explain the rationale to me?  Not that it matters a damn. 
Just idle curiosity.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276