R help - Mar 2005 - Trouble with expression() in R-win 2.0.1

Hi.
   The following statement works fine in R-win 1.8.0, but yields a syntax
   error in R-win 2.0.1 (and possibly in other versions after 1.8.0):

     plot(c(1,2),main=expression(a==b==c))

   I  note  that  the  following workaround executes successfully in both
   versions of R...

     plot(c(1,2),main=expression(a*"="*b*"="*c))

   ...but  I don't really understand why the first version works in 1.8.0
   and not in 2.0.1.
   Yours truly,
   Ronnen.
   P.S. E-mailed CCs of posted replies appreciated.
-- 
Ronnen Levinson, Ph.D.            \/      [1]RML27 at cornell.edu
scientist                         ||      [2]http://ronnen.com
Lawrence Berkeley National Lab    /\      fax 425.955.1992

=====================================Men in colored shirts and seersucker suits,
women in slacks and midriff dresses
 displaying various grades of abdomen, moved in and out of California Spanish s
hops and office buildings. Nobody looked at the mountains standing above the to
wn, but the mountains were there, making them all look silly.

-- Ross Macdonald, "The Moving Target"
=====================================
References

   1. mailto:RML27 at cornell.edu
   2. http://ronnen.com/

On Friday 25 March 2005 20:26, Ronnen Levinson wrote:
>    Hi.
>    The following statement works fine in R-win 1.8.0, but yields a
> syntax error in R-win 2.0.1 (and possibly in other versions after
> 1.8.0):
>
>      plot(c(1,2),main=expression(a==b==c))
>
>    I  note  that  the  following workaround executes successfully in
> both versions of R...
>
>      plot(c(1,2),main=expression(a*"="*b*"="*c))
>
>    ...but  I don't really understand why the first version works in
> 1.8.0 and not in 2.0.1.
The relevant NEWS entry says:

    o   R no longer accepts associative use of relational operators.
        That is, 3 < 2 < 1 (which used to evalute as TRUE!) now causes
        a syntax error.  If this breaks existing code, just add
        parentheses -- or braces in the case of plotmath.

i.e., you want

plot(c(1,2),main=expression(a=={b==c}))

Deepayan