exactly like that! thanks a lot. Aurelien
2011/12/4 Felipe Carrillo <mazatlanmex...@yahoo.com> > Like this? > library(plyr) > ddply(df,.(comn,mi),summarise,stDEV=sd(x)) > > Felipe D. Carrillo > Supervisory Fishery Biologist > Department of the Interior > US Fish & Wildlife Service > California, USA > http://www.fws.gov/redbluff/rbdd_jsmp.aspx > > *From:* Aurélien PHILIPPOT <aurelien.philip...@gmail.com> > *To:* R-help@r-project.org > *Sent:* Sunday, December 4, 2011 12:32 PM > *Subject:* [R] Group several variables and apply a function to the group > > Dear R-experts, > I am struggling with the following problem, and I am looking for advice > from more experienced R-users: I have a data frame with 2 identifying > variables (comn and mi), and an output variable (x). comn is a variable for > a company and mi is a variable for a month. > > comn<-c("abc", "abc", "abc", "abc", "abc", "abc", "xyz", "xyz","xyz", > "xyz") > mi<- c("1", "1","1", "2", "2", "2", "1", "1", "3", "3") > x<- c("-0.0031", "0.0009", "-0.007", "0.1929","0.0087", "0.099","-0.089", > "0.005", "-0.0078", "0.67" ) > df<- data.frame(comn=comn, mi=mi, x=x) > > > For each company, within a particular month, I would like to compute the > standard deviation of x: for example, for abc, I would like to compute the > sd of x for month1 (when mi=1) and for month2 (when mi=2). > > In other languages (Stata for instance), I would create a grouping variable > (group comnn and mi) and then, apply the sd function for each group. > > However, I don't find an elegant way to do the same in R: > > I was thinking about the following: I could subset my data frame by mi and > create one file per month, and then make a loop and in each file, use a > "by" operator for each comn. I am sure it would work, but I feel that it > would be like killing an ant with a tank. > > I was wondering if anyone knew a more straightforward way to implement that > kind of operation? > > Thanks a lot, > > Best, > Aurelien > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > > [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
