>(I don't recall any Prime Minister called Johnson or Nixon, by the way...)
That's why the variable was called "president". "prime.minister" is four letters and a dot longer. That was too complicated ;) ------------------------- cuncta stricte discussurus ------------------------- -----Ursprüngliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Gesendet: Sunday, March 30, 2008 11:50 PM An: [EMAIL PROTECTED]; [EMAIL PROTECTED]; r-help@r-project.org Betreff: RE: [R] Finding a mean value of a variable holding a dummyvariablefixed Here is another way, starting with similar dummy data: ____________ PMData <- data.frame(PM = c("Thatcher", "Thatcher", "Thatcher", "Thatcher", "Thatcher", "Thatcher","Major", "Major", "Major", "Major", "Major", "Major"), approval = c(3, 4, 5, 6, 7, 8, 6, 5, 4, 3, 2, 1)) PMData <- transform(PMData, Month = 1:nrow(PMData)) ## add the time variable PM_average <- with(PMData, tapply(approval, PM, mean)) PM_span <- with(PMData, sapply(tapply(Month, PM, range), function(x) structure(approval[Month[x]], names = c("First", "Last")))) ____________ > rbind(mean = PM_average, PM_span) Major Thatcher mean 3.5 5.5 First 6.0 3.0 Last 1.0 8.0 (I don't recall any Prime Minister called Johnson or Nixon, by the way...) Bill Venables CSIRO Laboratories PO Box 120, Cleveland, 4163 AUSTRALIA Office Phone (email preferred): +61 7 3826 7251 Fax (if absolutely necessary): +61 7 3826 7304 Mobile: +61 4 8819 4402 Home Phone: +61 7 3286 7700 mailto:[EMAIL PROTECTED] http://www.cmis.csiro.au/bill.venables/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Daniel Malter Sent: Monday, 31 March 2008 1:22 PM To: 'Alexander Ovodenko'; r-help@r-project.org Subject: Re: [R] Finding a mean value of a variable holding a dummyvariablefixed I found a solution. It's probably not the easiest one, but it works. It assumes that your data frame is ordered from earliest to latest record for each president, but it can be easily adjusted if you want to make it dependent on a third column. The final vector "index" gives you the line indices for the first record for each president. If you replace "min" by "max" you get the last instead of the first record. You can then find the values by ##Sample data president=c("Johnson","Johnson","Johnson","Johnson","Johnson","Johnson","Nix on","Nixon","Nixon","Nixon","Nixon","Nixon") approval=c(3,4,5,6,7,8,6,5,4,3,2,1) tapply(approval,president,mean) ##Find index for first row of each president; assumes ascending order of observations; change "min" to "max" to find last record index=NULL for(i in 1:length(unique(president))) index[i]=min(which((president==unique(president)[i])==TRUE)) index ##Generate table with first approvals first.approval=data.frame(cbind(index,president[index],approval[index])) names(first.approval)=c("Index","President","Approval") first.approval Cheers, Daniel ------------------------- cuncta stricte discussurus ------------------------- -----Ursprüngliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von Alexander Ovodenko Gesendet: Sunday, March 30, 2008 9:47 PM An: r-help@r-project.org Betreff: [R] Finding a mean value of a variable holding a dummy variablefixed I have time-series data on approval ratings of British Prime Ministers. The prime ministers dating from MacMillan onward till today are coded as dummy variables and the approval ratings are entered for each month. I want to know the mean value of the approval rating of each Prime Minister in the dataset and the approval rating during his/her first month and last month as PM. What R code should I enter for these data? In other words, I want hold the dummy corresponding to each Prime Minister fixed at value one and know the first rating that PM has, the last rating s/he has, and the mean rating s/he has. Thanks. [[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. ______________________________________________ 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. ______________________________________________ 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.
