[R] about sorting table

Uwe Ligges ligges at statistik.uni-dortmund.de
Thu Dec 1 10:33:07 CET 2005


Martin Maechler wrote:

>>>>>>"UweL" == Uwe Ligges <ligges at statistik.uni-dortmund.de>
>>>>>>    on Thu, 01 Dec 2005 08:37:37 +0100 writes:
> 
> 
>     UweL> herodote at oreka.com wrote:
>     >> hi all,
>     >> 
>     >> I load a table with headers that enable me to acces it by the column names:
>     >> 
>     >> tab<-read.table("blob/data.dat",h=T)
>     >> attach(tab)
>     >> 
>     >> everythings are OK, but i try to sort this table against one of his column like this:
>     >> 
>     >> tab<-tab[order(tab$IndexUI),];
>     >> 
>     >> It is still ok, the table is sorted, if i type "tab" i see a sorted table.
>     >> 
>     >> but, when i call the column by their names, it appears that the column isn't sorted...
>     >> 
>     >> I believe that, is there a solution to attach column names another time, to reflect the effect of sorting this table?
>     >> 
>     >> thks all for your answers
> 
>     UweL> see ?colnames
> 
> eehm, that won't really help here.
> 
> The problem is that Guillaume
> - first attach()ed the data frame

Ah, thank you, MArtin, I overlooked that line ....

Uwe


> - then changed the data frame itself,
> - and then erronously assumed that the *attached* data would change.
> 
> In general, we nowadays recommend quite often against using attach()
> but rather use the 'data = ' argument where applicable and use
> with( <data frame> , <......> ) 
> otherwise.
> 
> Martin Maechler, ETH Zurich




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