How about: with(dat, tapply(HR, SUBJECT_ID, sd))
Assuming your data frame is named dat. On Wed, 2008-11-19 at 23:59 -0500, pufftissue pufftissue wrote: > *Hi all, > > I know this is probably basic, but I have proven to be a slow learner in any > programming language. Anyhow, > how can I calculate the SD for each person in my table? I have two patients > in this R data.frame, 7200 and 23955. > I extracted this from a relational database, but am I better off attempting > to compute SD in SQL, or is this easily accomplished in R? > > > * SUBJECT_ID HR > 1 7200 158 > 2 7200 165 > 3 7200 138 > 4 7200 152 > 5 7200 139 > 6 7200 157 > 7 7200 186 > 8 23955 167 > 9 23955 162 > 10 23955 171 > 11 23955 139 > 12 23955 170 > 13 23955 177 > 14 23955 180 > 15 23955 176 > 16 23955 172 > 17 23955 179 > 18 23955 181 > 19 23955 169 > 20 23955 168 > 21 23955 185 > 22 23955 181 > 23 23955 191 > 24 23955 179 > 25 23955 178 > 26 23955 184 > 27 23955 179 > 28 23955 172 > 29 23955 173 > 30 23955 182 > 31 23955 174 > > * > So, what I would want is a table of 800 patients with a SD for their heart > rates: > > subject id Heart Rate SD > > 7200 20 (for example) > 23955 18 (for example)* > > Thank you! > > [[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. -- Simon Blomberg, BSc (Hons), PhD, MAppStat. Lecturer and Consultant Statistician Faculty of Biological and Chemical Sciences The University of Queensland St. Lucia Queensland 4072 Australia Room 320 Goddard Building (8) T: +61 7 3365 2506 http://www.uq.edu.au/~uqsblomb email: S.Blomberg1_at_uq.edu.au Policies: 1. I will NOT analyse your data for you. 2. Your deadline is your problem. The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. - John Tukey. ______________________________________________ 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.