1. This is a question about statistical methodology, not R. Hence inappropriate here.
2. Replies should therefore be private. 3. Consult the literature. Cheers, Bert Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." Clifford Stoll On Thu, Jun 19, 2014 at 6:23 PM, Rich Shepard <[email protected]> wrote: > I have several small biological count-based data sets with one or more > rows having zero proportion. The other proportions in the row sum to 1.000 > (or 0.9999 in the sixth data row below because of rounding errors in the > computer). An example is: > > sampdate filter gather graze predate shred > 2000-07-18 0.0550 0.5596 0.0734 0.2294 0.0826 > 2003-07-08 0.0734 0.6147 0.0183 0.2294 0.0642 > 2005-07-13 0.1161 0.5714 0.0357 0.1696 0.1071 > 2006-06-28 0.1000 0.4667 0.1500 0.1333 0.1500 > 2010-09-14 0.0778 0.6111 0.0444 0.1889 0.0778 > 2011-07-13 0.0879 0.5714 0.0659 0.2747 0.0000 > 2012-07-11 0.1042 0.5313 0.0625 0.2396 0.0625 > > My concern is that in most field-biological (ecological/environmental) > data there can be two explanations for zero counts: the organism was not > present on that date or it was present but not collected. There is no way to > determine which case holds true in each instance, but the ecological > interpretations differ. > > The zCompositions package offers several methods of imputing a value to > replace the zeros. As I'm completely new to compositional data analyses > (CoDA) I would appreciate advice on how to select the most appropriate > method for these data sets. The available methods are: Geometric Bayesian > multiplicative, BM, (GBM, default); square root BM (SQ); Bayes-Laplace BM > (BL); count zero multiplicative (CZM); user-specified hyper-parameters > (user). > > These biological data seem to me to be different from geochemical or > economic data I see in package data sets or the CoDA references I've > acquired and read. > > Advice and suggestions (including references to application of CoDA to > ecological/environmental data) will be appreciated. > > Rich > > ______________________________________________ > [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. ______________________________________________ [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.
