On Wed, 31 Aug 2011, Tal Galili wrote:
It is a bit hard to read the "summary" you are using. Consider please pasting the output of: ls.str(chemdata)
Tal, Yes, summary() is inappropriate. I do want str() instead. And what that shows is:
str(chemdata)
'data.frame': 14886 obs. of 1 variable: $ site_id.sample_date.param.quant: Factor w/ 14886 levels "BC-0.5|1996-04-19|Arsenic|0.01",..: 11579 14219 13298 11982 11909 13371 13082 111 12 23 ...
Regarding your question, please start and see if this work (I'm not sure, since it seems you have made some changes to the summary output, and I am only guessing how things look):
mean(chemdata$quant[chemdata$param > =="Arsenic"])
mean(chemdata$quant[chemdata$param > =="Arsenic"])
Error: unexpected '==' in "mean(chemdata$quant[chemdata$param > =="
mean(chemdata$quant[chemdata$param =="Arsenic"])
[1] NA Warning message: In mean.default(chemdata$quant[chemdata$param == "Arsenic"]) : argument is not numeric or logical: returning NA I find it easy following the syntax in the half-dozen or more books I've read, but quite difficult to apply what I read to my own real-world data. :-) Thanks, Rich ______________________________________________ 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.
