Re: [R] about sorting table

From: Uwe Ligges <ligges_at_statistik.uni-dortmund.de>
Date: Thu 01 Dec 2005 - 20:33:07 EST

Martin Maechler wrote:

>>>>>>"UweL" == Uwe Ligges <ligges@statistik.uni-dortmund.de>
>>>>>>    on Thu, 01 Dec 2005 08:37:37 +0100 writes:

>
>
> UweL> herodote@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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