Brian, If I do understand correctly, I must use in my function something else than ddply() if I want to avoid any error each time my df has zero rows? Am I correct?
TY > -----Original Message----- > From: Prof Brian Ripley [mailto:rip...@stats.ox.ac.uk] > Sent: Tuesday, June 01, 2010 9:47 AM > To: arnaud Gaboury > Subject: Re: [R] data frame manipulation with zero rows > > On Tue, 1 Jun 2010, arnaud Gaboury wrote: > > > Dear group, > > > > Here is the kind of data.frame I obtain every day with my function : > > > > futures <- > > structure(list(DESCRIPTION = c("CORN Jul/10", "CORN Jul/10", > > "CORN Jul/10", "CORN Jul/10", "CORN Jul/10", "LIVE CATTLE Aug/10", > > "LIVE CATTLE Aug/10", "SUGAR NO.11 Jul/10", "SUGAR NO.11 Jul/10", > > "SUGAR NO.11 Jul/10", "SUGAR NO.11 Jul/10", "SUGAR NO.11 Jul/10" > > ), CREATED.DATE = structure(c(18403, 18406, 18406, 18406, 18406, > > 18407, 18408, 18406, 18407, 18407, 18407, 18407), class = "Date"), > > QUANTITY = c(1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1), SETTLEMENT = > > c("373.2500", > > "373.2500", "373.2500", "373.2500", "373.2500", "90.7750", > > "90.7750", "14.9200", "14.9200", "14.9200", "14.9200", "14.9200" > > )), .Names = c("DESCRIPTION", "CREATED.DATE", "QUANTITY", > > "SETTLEMENT"), row.names = c(NA, 12L), class = "data.frame") > > > > I need then to apply to the df this following code line : > > > >> PosFut=ddply(futures, c("DESCRIPTION","SETTLEMENT"), summarise, > POSITION= > > sum(QUANTITY))[,c(1,3,2)] > > > > It works perfectly in most of case, BUT I have a new problem: it can > > sometime occurs that my df "futures" is empty, with zero rows. > > > > > > futures <- > > structure(list(DESCRIPTION = character(0), CREATED.DATE = > > structure(numeric(0), class = "Date"), > > QUANTITY = numeric(0), SETTLEMENT = character(0)), .Names = > > c("DESCRIPTION", > > "CREATED.DATE", "QUANTITY", "SETTLEMENT"), row.names = integer(0), > class = > > "data.frame") > > > > It is not the usual case, but it can happen. With this df, when I > pass the > > above mentione line, I get an error : > > > >> PosFut=ddply(futures, c("DESCRIPTION","SETTLEMENT"), summarise, > POSITION= > > sum(QUANTITY))[,c(1,3,2)] > > Error in tapply(1:nrow(data), splitv, list) : > > arguments must have same length > > > > > > How can I avoid this when my df is empty? > > Ask the author of the (missing) function ddply() to correct the error > of using 1:nrow(data) by replacing it by seq_len(nrow(data)). > > It's helpful to give example code, but much more helpful if you test > it: yours cannot work without the function ddply() -- this is what > 'self-contained' means in the footer here. > > > > > > Any help is appreciated > > > > ______________________________________________ > > 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. > > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ 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.
