On Wed, 16 Feb 2005, Robin Hankin wrote:
The following caught me off-guard:
R> z <- 1i + 1:10 R> z <- Re(z) R> z [1] 1 2 3 4 5 6 7 8 9 10
as expected. But look:
R> z <- 1i + 1:10 R> make.real <- abs(z) < 1000 R> z[make.real] <- Re(z[make.real]) R> z [1] 1+0i 2+0i 3+0i 4+0i 5+0i 6+0i 7+0i 8+0i 9+0i 10+0i R>
didn't make z a real vector, which is what I wanted. ?"[<-" says
If one of these expressions appears on the left side of an assignment then that part of 'x' is set to the value of the right hand side of the assignment.
so the behaviour is as documented: class(z) is unchanged in the second session.
Would modifying "[<-" to add a test for all elements of an object being replaced (and if this is the case to change the class of z appropriately), be a bad idea?
Yes. Don't expect your interpreter to mind-read. Changing basic things like this is likely to break lots of existing code.
R-help is not really the place for programming design questions (R-devel is).
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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