I am trying to calculate monthly means by year of phosphates and nitrates from a multi year data set. Can anybody help me out with the most effective way to do this?
My data looks like this: Collection_Date Test.Name Value 2000-01-24 17:00:00 Phosphate 0.108 2000-01-24 17:00:00 Nitrate 0.037 2001-11-12 08:45:00 Phosphate 0.45 ... Thanks and sorry for the blatantly "newbie" question. [[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.