summing values by group
you could use '?by()', e.g., dat <- data.frame(CAT=sample(letters[1:5], 100, TRUE), x=rnorm(100), y=rnorm(100), z=rnorm(100)) by(dat[sapply(dat, is.numeric)], dat$CAT, sum) by(dat[sapply(dat, is.numeric)], dat$CAT, mean) I hope it helps. Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/16/336899 Fax: +32/16/337015 Web: http://www.med.kuleuven.ac.be/biostat/ http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm ----- Original Message ----- From: "Larry White" <ljw1001 at gmail.com> To: <R-help at stat.math.ethz.ch> Sent: Thursday, March 24, 2005 5:12 PM Subject: [R] summing values by group
At the risk of being wacked for asking what should be obvious.... I have a data frame with one categorical variable "CAT" and several numeric variables. I want to be able to get simple statistics on the numeric variables by level. For example, just as you can use table (CAT) to get the counts, I'd like to be able to get the means and sums by category. If someone could point me in the right direction, I'd appreciate it. I've been through the SimpleR and Using R for Data Analysis... docs and I'm still clueless. thanks for your help.
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