I am transitioning from SAS to R and am struggling with a relatively simple analysis. Have tried Venables and Ripley and other guides but can't find a solution.
I have an experiment with 12 tanks. Each tank holds 10 fish. The 12 tanks have randomly assigned one of 4 food treatments - S(tarve), L(ow), M(edium) and H(igh). There are 3 reps of each treatment. I collect data on size of each fish at the end of the experiment. So my data looks like Tank Trt Fish Size 1 S 1 3.4 1 S 2 3.6 .... 1 S 10 3.5 2 L 1 3.4 .... 12 M 10 2.1 To do the correct test of hypothesis using anova, I need to calculate the tank means and use those in the anova. I have tried using tapply() and by() functions, but when I do so I "loose" the treatment level because it is categorical. I have used Meandat<tapply(Size,list(Tank, Trt), mean) But that doesn't give me a dataframe that I can then use to do the actual aov analysis. So what is the most efficient way to accomplish the analysis Thanks Tom Miller ______________________________________________ [email protected] 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.
