[Rd] rowsum() may return a vector instead of a matrix (PR#3737)

[brahm at alum.mit.edu]

If all rows are in the same "group", rowsum() returns a vector instead of a
(1xN) matrix, contrary to documentation:

R> print(z <- rowsum(matrix(1:12, 3,4), rep("x",3)))
   [1]  6 15 24 33
R> dim(z)
   NULL

It worked correctly in version 1.4.0 but was broken by version 1.6.1.  I'm
currently using 1.7.1 under Solaris 2.8.


--please do not edit the information below--

Version:
 platform = sparc-sun-solaris2.8
 arch = sparc
 os = solaris2.8
 system = sparc, solaris2.8
 status = 
 major = 1
 minor = 7.1
 year = 2003
 month = 06
 day = 16
 language = R

Search Path:
 .GlobalEnv, package:misc, package:io, package:arrays, package:ls1, package:obsi, package:g.data, package:db, package:ts, package:ctest, Autoloads, package:base
-- 
                              -- David Brahm (brahm at alum.mit.edu)