From: Heinz Tuechler <tuechler_at_gmx.at>

Date: Thu 11 Aug 2005 - 01:10:13 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Aug 11 01:17:44 2005

Date: Thu 11 Aug 2005 - 01:10:13 EST

Dear Professor Ripley,

thank you for your answer. Adding a return value, as also Dimitris
Rizopoulos suggested the function does what I need, that is to rename
factor levels.

I tried to look at levels<-.factor in R-devel but I have to admit that I do
not know exactly where to look and searching I did not find it. For the
moment my problem is solved and I interpret your hint that way that in the
future levels<-.factor will not more drop all other attributes.

Thanks again

Heinz Tüchler

At 15:18 10.08.2005 +0100, Prof Brian Ripley wrote:

>On Wed, 10 Aug 2005, Heinz Tuechler wrote:

*>
**>> where can I find information about how to write an assigment form of a
**>> function?
**>
**>In all good books on S programming, or by studying examples. But in this
**>case the problem is actually about defining functions with the return
**>value you expect.
**>
**>> For curiosity I tried to write a different form of the levels()-function,
**>> since the original method for factor deletes all other attributes of a
*

factor.

>> Of course, the simple method would be to use instead of levels(x) <-

*>> newlevels, attr(x, 'levels') <- newlevels.
**>
**>And that would not do what the current function does, which is to merge
**>levels as required.
**>
**>I suggest you look at levels<-.factor in R-devel, which does not drop
**>attributes.
**>
**>
**>> I tried the following:
**>> ## example
**>> x <- factor(c(1,1,NA,2,3,4,4,4,1,2)); y <- x
**>> attr(x, 'levels') <- c('a', 'b', 'c', 'd') # does what I want
**>> x
**>> [1] a a <NA> b c d d d a b
**>> Levels: a b c d
**>>
**>> 'levels.simple<-' <- function (x, value)
**>> {
**>> attr(x, 'levels') <- value
**>> }
**>
**>This did not return anything! Try returning 'x'.
**>
**>> levels.simple(y) <- c('a', 'b', 'c', 'd') # does not what I want
**>> y
**>> [1] "a" "b" "c" "d"
**>
**>
**>--
**>Brian D. Ripley, ripley@stats.ox.ac.uk
**>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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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Aug 11 01:17:44 2005

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