From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>

Date: Mon 13 Feb 2006 - 21:54:21 EST

Date: Mon 13 Feb 2006 - 21:54:21 EST

- The obvious test is via is.factor(), and you have not used that.
- Your example works for me, so what versions of R and chron is this?
- Here's my guess. split is using the C-level test isFactor. That tests that the factor is of type integer, so please try

*> typeof(kvartaly)
*

I suspect you will get "double" and not "integer", and if so you can fix this by

storage.mode(kvartaly) <- "integer"

So here's an example which will fail

*> fac2 <- rep(c(1,2,3), each=5)
**> attr(fac2, "levels") <- as.character(1:3)
**> oldClass(fac2) <- "factor"
**> is.factor(fac2)
*

**[1] TRUE
**

*> split(rnorm(15), fac2)
*

Error in split(x, f) : second argument must be a factor

I think it is an error that the R-level and C-level tests for is.factor() are different.

On Mon, 13 Feb 2006, Petr Pikal wrote:

> Hallo all

*>
**> Please help me. I am lost and do not know what is the problem. I have
**> a factor called kvartaly.
**>
**>> attributes(kvartaly)
**> $levels
**> [1] "1Q.04" "2Q.04" "3Q.04" "4Q.04" "1Q.05" "2Q.05" "3Q.05" "4Q.05"
**> $class
**> [1] "factor"
**>> mode(kvartaly)
**> [1] "numeric"
**>> str(kvartaly)
**> Factor w/ 8 levels "1Q.04","2Q.04",..: 1 1 1 1 1 1 1 1 1 1 ...
**>>
**>
**> but if I call split it throws an error
**>
**>> split(rnorm(731),kvartaly)
**> Error in split(x, f) : second argument must be a factor
**>
**> so I tried to make a test example which works if I try to construct
**> factor manually but fails if I use chron
**>
**> vec<-c("1Q.04", "1Q.05", "1Q.06")
**> fac<-as.factor(rep(vec,c(5,5,5)))
**>
**> split(rnorm(15),fac)
**> $"1Q.04"
**> [1] 1.9803999 -0.3672215 -1.0441346 0.5697196 -0.1350546
**>
**> $"1Q.05"
**> [1] 2.40161776 -0.03924000 0.68973936 0.02800216 -0.74327321
**>
**> $"1Q.06"
**> [1] 0.1887923 -1.8049586 1.4655549 0.1532533 2.1726117
**>
**> vec1<-as.Date(Sys.time())
*

> vec1<-c(vec1, vec1-100, vec1-300)

*> vec1<-rep(vec1,c(5,5,5))
**> fac1<-interaction(quarters(as.chron(as.POSIXct(vec1))),
**> format(vec1,"%y"))
**>> split(rnorm(15),fac1)
**> Error in split(x, f) : second argument must be a factor
**> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
**>
**> Why split does not accept fac1 if according to all tests it **is** a
**> factor?
**>
**> Thank you
**> Petr
**>
**> Petr Pikal
**> petr.pikal@precheza.cz
*

-- 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 ______________________________________________ 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.htmlReceived on Mon Feb 13 22:01:05 2006

*
This archive was generated by hypermail 2.1.8
: Fri 03 Mar 2006 - 03:42:29 EST
*