tapply changing order of factor levels?

Hi Alain,

I tried levels(myfactor) as you suggested.

levels(myfactor)

[1] "IN0020020155" "IN0019800021" "IN0020020064"

The order is preserved, no alphanumerical sorting done here.
Regards.

On Wed, May 6, 2009 at 7:35 PM, Alain Guillet 
<alain.guillet at uclouvain.be <mailto:alain.guillet at uclouvain.be>> wrote:

    Hi,

    I don't believe the problem is related to tapply. I would say it
    is because of the factor. In fact, the order of a factor is given
    by the alphanumerical order of his levels. You can see it with
    levels(myfactor).
    I you want to change the order, redefine the levels of myfactor
    with the expected order or use the function ordered.

    Alain


    Chirantan Kundu wrote:

        Hi,

        Does tapply change the order when applied on a factor? Below
        is the code I
        tried.

         

            mylevels<-c("IN0020020155","IN0019800021","IN0020020064")

               

        mydata<-c("IN0020020155","IN0019800021","IN0020020064","IN0020020155","IN0019800021","IN0019800021","IN0020020064","IN0020020064","IN0019800021")
         

            myfactor<-factor(mydata,levels=mylevels)
            myfactor
               

        [1] IN0020020155 IN0019800021 IN0020020064 IN0020020155
        IN0019800021
        IN0019800021 IN0020020064 IN0020020064 IN0019800021
        Levels: IN0020020155 IN0019800021 IN0020020064
         

            summary(myfactor)
               

        IN0020020155 IN0019800021 IN0020020064
                  2            4            3

        # Everything fine upto this point. The order of levels is
        maintained as it
        is.

         

            mysummary<-tapply(myfactor,mydata,length)
            mysummary
               

        IN0019800021 IN0020020064 IN0020020155
                  4            3            2

        # Now the order has changed.

        Is this the expected behavior? Any idea on how to avoid the
        change in order?

        Regards,
        Chirantan