one way is with ave(), e.g.,
dat <- data.frame(name = rep(c("Mary", "Sam", "John"), c(3,2,4)))
dat$freq <- ave(seq_along(dat$name), dat$name, FUN = seq_along)
dat
I hope it helps.
Best,
Dimitris
jie feng wrote:
Hi, there,
I have a simple data manipulation question for you. Thank you for your help!
Suppose that I have this data about people appearing in a class
Mary
Mary
Mary
Sam
Sam
John
John
John
John
Then I want to find out what exact time(s) the student appears at the
moment such as
Mary 1
Mary 2
Mary 3
Sam 1
Sam 2
John 1
John 2
John 3
John 4
the fifth row shows tha Sam show the second times at the that moment.
How can I manipulate the data in this way. Suppose that now I just have
"name" variable and want to add a colume of frequency?
Best
Jie
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--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
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and provide commented, minimal, self-contained, reproducible code.
