From: Antonio, Fabio Di Narzo <antonio.fabio_at_gmail.com>

Date: Fri 19 May 2006 - 00:04:08 EST

x <- rnorm(10)

dat <- data.frame(x=x, v1=v1, v2=v2)

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Fri May 19 00:10:36 2006

Date: Fri 19 May 2006 - 00:04:08 EST

Hi all.

I have a pure R programming question.

Having a data.frame with a 'data' variable and some (>1) ID variables

(either numeric or factors), I would extract a sequence of data values given

a sequence of ID values.

Here's an example. Build a dataset:

n1 <- 5 n2 <- 2 v1 <- rep(factor(1:n1),2) v2 <- rep(1:n2,5)

x <- rnorm(10)

dat <- data.frame(x=x, v1=v1, v2=v2)

Now, for example, I should extract x values responding to some arbitrary
IDs:

(v1="2", v2=1), (v1="3", v2=2), (v1="4", v2=1).

For example, I should store those id sequences in a separate list (maybe an
indexing data.frame), but this really isn't the point.
The point is that I have somewhere a ready sequence of IDs from which
obtaining corresponding data.

Note that I don't know if some ID combination exists in the database.
Some suggestions on a good way to do this?

Tnx all,

Antonio, Fabio Di Narzo.

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