Try tapply(). For example:
tapply(data$Nitrogen,factor(data$Species),mean) For the Nitrogen column, the mean is calculated for each Species. (if the data frame below is in the object data) Regards, Annemarie Eigenhuis -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Ramsvatn Silje Sent: donderdag 4 november 2010 13:28 To: R-help@r-project.org Subject: [R] Sorting data from one column with strings Hello, I have tried to find this out some other way, but unsuccessful I have to try this list. I assume this should be quite simple. I have a dataset with 4 columns, "Sample_no", "Species", "Nitrogen", "Carbon" in csv format. In the species column I have many different species with varying number of obs per species Eg "Sample_no" "Species" "Nitrogen" "Carbon" 1 Cod 15.2 -19.0 2 Haddock 14.8 -20.2 3 Cod 15.6 -18.5 4 Cod 13.2 -20.1 5 Haddock 14.3 -18.8 Etc.. And I want to calculate, mean, standard dev etc per species for the observations "Nitrogen" and "Carbon". And later do plots and stats with the different species. I will in the end have many species, so need it to be "automatic" I can't enter code for every species separate. Can anyone help me with this? Or if this is the wrong list to sendt this question to, where do I send it? Thank you very much in advance. Best regards Silje Ramsvatn PhD-candidate University of Tromsø Norway ______________________________________________ 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. ______________________________________________ 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.
