about sorting table

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

guillaume.