On Thu, Jul 15, 2010 at 12:52 AM, Meissner, Tony (DFW) <tony.meiss...@sa.gov.au> wrote: > I have a data frame (morgan) of hourly river flow, river levels and wind > direction and speed thus: > Time hour lev.morgan lev.lock2 lev.lock1 flow direction > velocity > 1 2009-07-06 15:00:00 15 3.266 3.274 3.240 1710.6 180.282 > 4.352 > 2 2009-07-06 16:00:00 16 3.268 3.272 3.240 1441.8 192.338 > 5.496 > 3 2009-07-06 17:00:00 17 3.268 3.271 3.240 1300.1 202.294 > 2.695 > 4 2009-07-06 18:00:00 18 3.267 3.274 3.241 1099.1 237.161 > 2.035 > 5 2009-07-06 19:00:00 19 3.265 3.277 3.243 986.6 237.576 > 0.896 > 6 2009-07-06 20:00:00 20 3.266 3.281 3.242 1237.6 205.686 > 1.257 > 7 2009-07-06 21:00:00 21 3.267 3.280 3.242 1513.3 26.080 > 0.664 > 8 2009-07-06 22:00:00 22 3.267 3.281 3.242 1819.5 264.280 > 0.646 > 9 2009-07-06 23:00:00 23 3.267 3.281 3.242 1954.4 337.137 > 0.952 > 10 2009-07-07 00:00:00 0 3.267 3.281 3.242 1518.9 260.006 > 0.562 > 11 2009-07-07 01:00:00 1 3.267 3.281 3.242 1082.6 252.172 > 0.673 > 12 2009-07-07 02:00:00 2 3.267 3.280 3.243 1215.9 190.007 > 1.286 > 13 2009-07-07 03:00:00 3 3.267 3.279 3.244 1093.5 260.415 > 1.206 > : : : : : : : : > : > : : : : : : : : > : >
There are many possibilities. Here are three. #1 can be done with only the core of R. #2 produces a zoo series which seems to be the logical representation since it is, in fact, a series so its now already in the form for other series operations. See the 3 vignettes that come with zoo. with #3 its easy to take different functions (avg, count, etc.) of different columns and if you already know SQL its particularly convenient. See http://sqldf.googlecode.com # DF2 is used in #1 and #3 DF2 <- data.frame(DF, Day = as.Date(format(DF$Time))) # 1 - aggregate aggregate(cbind(flow, direction, velocity) ~ Day, DF2, mean) # 2 - zoo library(zoo) z <- read.zoo(DF, header = TRUE, tz = "GMT") aggregate(z, as.Date, mean) # 3 - sqldf library(sqldf) sqldf("select Day, avg(flow) Flow, avg(direction) Direction, avg(velocity) Velocity from DF2 group by Day") ______________________________________________ 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.
