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@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
>>
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>>
>
> --
> Alain Guillet
> Statistician and Computer Scientist
>
> SMCS - Institut de statistique - Université catholique de Louvain
> Bureau d.126
> Voie du Roman Pays, 20
> B-1348 Louvain-la-Neuve
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>
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