Hi, I have a data frame and would like to have summary statistics for grouped data. With summary() I get the central tendencies for the overall data. How can I get descriptive statistics with variances and standard deviations? for example my data.frame: group x y exp 2 4 exp 3 5 exp 2 4 control 1 2 control 2 3 control 1 2 now I want tables with summary statistics (variances included) for each group. Is there an easy way to get this?
Hi J?rg, ?by here probably something like by(data=mydata,INDICES=mydata$group, FUN=sd, ...) HTH, Stephan J?rg Gro? schrieb:> Hi, > > I have a data frame and would like to have summary statistics for > grouped data. > > With summary() I get the central tendencies for the overall data. > > > How can I get descriptive statistics with variances and standard > deviations? > > > for example my data.frame: > > group x y > exp 2 4 > exp 3 5 > exp 2 4 > control 1 2 > control 2 3 > control 1 2 > > > now I want tables with summary statistics (variances included) for each > group. > > Is there an easy way to get this? > > ______________________________________________ > R-help at 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. >
You can use summaryBy() in the doBy package: summaryBy(y+x~group, data=mydata, FUN=c(mean,sd)) S?ren ________________________________ Fra: r-help-bounces at r-project.org p? vegne af J?rg Gro? Sendt: s? 11-01-2009 22:38 Til: r-help at r-project.org Emne: [R] summary with variance / sd Hi, I have a data frame and would like to have summary statistics for grouped data. With summary() I get the central tendencies for the overall data. How can I get descriptive statistics with variances and standard deviations? for example my data.frame: group x y exp 2 4 exp 3 5 exp 2 4 control 1 2 control 2 3 control 1 2 now I want tables with summary statistics (variances included) for each group. Is there an easy way to get this? ______________________________________________ R-help at 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.
On Jan 11, 2009, at 4:38 PM, J?rg Gro? wrote:> Hi, > > I have a data frame and would like to have summary statistics for > grouped data. > > With summary() I get the central tendencies for the overall data. > > > How can I get descriptive statistics with variances and standard > deviations?In the future, you really should do your own searching before posting this sort of basic question. help.search("standard deviation") produced reference to a function with the obvious name "sd" Using the same strategy for variance produces a longer list but "var" is among them.> for example my data.frame: > > group x y > exp 2 4 > exp 3 5 > exp 2 4 > control 1 2 > control 2 3 > control 1 2#Create dataframe ( and please note that you are asked to offer examples in a form that does not require responders to create the objects for you): df1 <- read.table(stdin(), header=TRUE) #Paste in the data: 0: group x y 1: exp 2 4 2: exp 3 5 3: exp 2 4 4: control 1 2 5: control 2 3 6: control 1 2 # empty line stops input. by(data=df1, df1$group, summary) by(data=df1, df1$group, sd) by(data=df1, df1$group, var) Or.... use negative indexing to exclude the first column, and add some annotation to do it in one step by(data=df1[-1], df1$group, function(x){ list(summary(x), "Group S.D.s are ...", sd(x), "Group Variances are ...", var(x) )} ) You could also look at how the pro's do constructed summary() by reviewing the code of: base:::summary.default base:::summary.data.frame -- David Winsemius> > > > now I want tables with summary statistics (variances included) for > each group. > > Is there an easy way to get this? > > ______________________________________________ > R-help at 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.