On Jan 24, 2015, at 8:37 AM, peter dalgaard wrote: > Don't worry, there are plenty of halfwits around here. However, this is about > stats theory, and not really about R, so you're better off trying > CrossValidated, aka stats.stackexchange.com
This is useful and correct advice, but if you want to see an excellent description of some of the R tools for dealing with zero-inflation, the Zeileis, Kleiber & Jackman article on the matter: http://www.jstatsoft.org/v27/i08/paper , was very helpful in advancing my understanding of the subject area. > > -pd > >> On 24 Jan 2015, at 14:26 , Ben Brooker <awe....@googlemail.com> wrote: >> >> Hi, >> >> I am new to R and have not had the most exposure to statistics. >> I have a dataset of percentage cover (so 0-100) for certain species in 3 >> different shore zones (High, mid and low). The data was recorded for >> different protected areas as well (17 of them) and my number of obs is >> large (3358). I'm obviously interested in the difference in percentage >> cover of species between shore zones as well as between protected areas. >> The problem is that my data contains loads of zeros and I haven't dealt yet >> in statistics with how to manipulate the data so as to perform robust tests >> on it. I previously used Kruskal-Wallis ANOVAs I wonder if the terms Kruskal-Wallis and ANOVA should be adjacent. I do not remember that variances are part of the inference with KW-tests. You might ask that in your question to the very helpful group on CrossValidated.com -- David. >> to look at cover differences >> in shore zone but I am worried that it is inappropriate because of the >> large sample size that I have and because my variances are not equal. >> >> I've read a bit about using a zero-inflated negative binomial regression to >> fit to my data, but I'm not sure if that will work because it is for count >> data. >> >> I would very much appreciate it if someone could point me in the correct >> direction wrt a transformation that may help or an appropriate model to fit >> or test to use. I've searched quite a bit but I'm a out of my depth. >> >> PS sorry if I sound like a halfwit >> >> Thanks a lot >> >> Ben >> ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
