Dear R Community, I am having some trouble with a task that I hope you might be able to help with. I have a dataset that includes the time and corresponding stream discharge from numerous storms (example of structure with simplified data below). I would like to produce a field that details the duration of each storm, where each storm is a subset of the data and the duration runs from zero to end for each unique storm. I have been trying to accomplish this with ddply but to no avail as I am unable to provide ddply (e.g., below) with the length of the storm (i.e., subset of data). Thank you in advance, any help would be appreciated.
existing df: storm,Q_time,Q s1,2008-08-07 21:15:00,0.000 s1,2008-08-07 21:16:00,3.020 s1,2008-08-07 21:17:00,6.041 s1,2008-08-07 21:18:00,9.061 s1,2008-08-07 21:19:00,12.082 s1,2008-08-07 21:20:00,15.102 s1,2008-08-07 21:21:00,18.123 s1,2008-08-07 21:22:00,11.143 s1,2008-08-07 21:23:00,0.000 s2,2010-10-05 21:00:00,0.000 s2,2010-10-05 21:01:00,1.812 s2,2010-10-05 21:02:00,3.625 s2,2010-10-05 21:03:00,5.437 s2,2010-10-05 21:04:00,7.249 s2,2010-10-05 21:05:00,9.061 s2,2010-10-05 21:06:00,0.874 s2,2010-10-05 21:07:00,0.000 desired df: storm,Q_time,Q, duration s1,2008-08-07 21:15:00,0.000,1 s1,2008-08-07 21:16:00,3.020,2 s1,2008-08-07 21:17:00,6.041,3 s1,2008-08-07 21:18:00,9.061,4 s1,2008-08-07 21:19:00,12.082,5 s1,2008-08-07 21:20:00,15.102,6 s1,2008-08-07 21:21:00,18.123,7 s1,2008-08-07 21:22:00,11.143,8 s1,2008-08-07 21:23:00,0.000,9 s2,2010-10-05 21:00:00,0.000,1 s2,2010-10-05 21:01:00,1.812,2 s2,2010-10-05 21:02:00,3.625,3 s2,2010-10-05 21:03:00,5.437,4 s2,2010-10-05 21:04:00,7.249,5 s2,2010-10-05 21:05:00,9.061,6 s2,2010-10-05 21:06:00,0.874,7 s2,2010-10-05 21:07:00,0.000,8 I have been trying variations of the following statement, but I cannot seem to get the length of the subset correct as I receive an error of the type 'Error: arguments imply differing number of rows: 2401, 0'. newdf <- ddply(df, "storm", transform, FUN = function(x) {duration=seq(from=1, by=1, length.out=nrow(x))}) I would really like to get a handle on ddply in this instance as it will be quite helpful for many other similar calculations that I need to do with this dataset. Thanks again, Stevan -- View this message in context: http://r.789695.n4.nabble.com/help-incorporating-data-subset-lengths-in-function-with-ddply-tp4688926.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.