[Rd] log( <ts object> ) is not <ts object> (PR#2315)

[maechler@stat.math.ethz.ch]

As I have found, taking functions like  log(.) on a "ts" object
returns something that still has the "ts" class attribute but is
not a properly classed R object anymore.

E.g.
	(lt <- log(as.ts(1:7)))

clearly calls  print.default instead of print.ts
and the analogue for  plot(lt)
or also
        diff(lt) 

returns a "ts" object but with invalid start/end.

(this is also a test of the R-bugs@R-project.org address)

Martin Maechler <maechler@stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO C16	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><