Message-ID: <4A019918.5000906@uclouvain.be>
Date: 2009-05-06T14:05:12Z
From: Alain Guillet
Subject: tapply changing order of factor levels?
In-Reply-To: <fc408ad80905060645k40deda53s668044a8ac95604b@mail.gmail.com>
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
>
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--
Alain Guillet
Statistician and Computer Scientist
SMCS - Institut de statistique - Universit? catholique de Louvain
Bureau d.126
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