Well, I knew that attach() only creates a copy of the variables in the
search path.
What I wanted to ask was how to *retrieve* that copy...
> mat
id age
1 NA NA
2 NA NA
3 NA NA
4 NA NA
5 NA NA
> attach(mat)
> id <<- sample(100,5)
> age <<- rnorm(5,mean=30)
How can I make a new data frame out of the id and age that were changed
above?
Hi
r-help-boun...@r-project.org napsal dne 10.02.2009 12:02:53:
Hello,
suppose I have a data frame:
mat
id age
1 NA NA
2 NA NA
3 NA NA
4 NA NA
5 NA NA
Then I attach the data frame:
attach(mat)
Look into docs what attach does. If you do not understand environments use
attach with great care
The database is not actually attached. Rather, a new environment is
created on the search path and the elements of a list (including columns
of a data frame) or objects in a save file or an environment are copied
into the new environment. If you use <<- or assign to assign to an
attached database, you only alter the attached copy, not the original
object. (Normal assignment will place a modified version in the user's
workspace: see the examples.) For this reason attach can lead to
confusion.
I assign some new values...
id <<- sample(100,5)
age <<- rnorm(5,mean=30)
Then I want to create a new data frame from the variables id and age
which
still are attached to position 2 of the R environment...
new_mat <- data.frame(ls(pos=2)) # I want to rescue ALL variables that
were
created by attach(mat)
new_mat
ls.pos...2.
1 age
2 id
But this leads to a bogus object... how can I rescue the updated id and
age
values into new_mat?
What about not using attach and transform mat directly
mat$age <- rnorm(5,mean=30)
mat$id <- sample(100,5)
mat
id age
1 24 29.17842
2 88 31.22606
3 32 30.81540
4 5 29.31528
5 11 29.32775
Regards
Petr
Regards,
David
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