Here is one way of doing it:
> x <- read.table(textConnection("subject hospital date_enrollment
hospital_beds
+ 1 hospitalA 1/3/2002 300
+ 2 hospitalA 1/6/2002 300
+ 3 hospitalB 2/4/2002 150
+ 4 hospitalC 3/2/2002 200"), header=TRUE)
> closeAllConnections()
> y <- as.Date(x$date_enrollment, "%m/%d/%Y")
> z <- cbind(x, year=format(y, "%Y"), month=format(y, "%m"))
> # partition the data
> z.s <- split(z, list(z$year, z$month, z$hospital), drop=TRUE)
> # now aggregate
> do.call(rbind, lapply(z.s, function(a) data.frame(hospital=a$hospital[1],
cases=nrow(a),
+ year=a$year[1], month=a$month[1], beds=a$hospital[1])))
hospital cases year month beds
2002.01.hospitalA hospitalA 2 2002 01 hospitalA
2002.02.hospitalB hospitalB 1 2002 02 hospitalB
2002.03.hospitalC hospitalC 1 2002 03 hospitalC
>
>
>
On Mon, Jun 9, 2008 at 12:45 PM, Ricardo Pietrobon <[EMAIL PROTECTED]>
wrote:
> I currently have a data set describing human subjects enrolled into an
> international clinical trial, the name of the hospital enrolling this
> human subject, the date when the subject was enrolled, and a vector
> with variables representing characteristics of the site (e.g., number
> of beds in a hospital). my data sets looks like this:
>
> subject hospital date_enrollment hospital_beds
> 1 hospitalA 1/3/2002 300
> 2 hospitalA 1/6/2002 300
> 3 hospitalB 2/4/2002 150
> 4 hospitalC 3/2/2002 200
>
> to perform a time series analysis I am now trying to get to a format
> that would give me the following variables:
>
> month year site number_enrolled_subjects hospital_beds
>
> the data would be displayed on one-month intervals, and number of
> subjects clustered around sites.
>
> any help would be greatly appreciate
>
> thanks
>
>
> Ricardo
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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