Hi, > I'm not sure how one would combine SEM / graphical models with compositional > dissimilarity as a response. You might be able to fit a series of models in > adonis() or capscale(), comparing just direct factors to direct + > intermediate, etc.. I don't have any good ideas on how you might test more > complex causal structures.
There's a fair bit of literature on Mantel-based path analysis, and other similar dissimilarity-based approaches. SEM can be used with composition as well, although not (I think) with the intermediate step of calculating dissimilarities. Besides journal articles employing those techniques, I like both of these: J. B. Grace, Structural Equation Modeling and Natural Systems, Cambridge University Press, Cambridge, UK, 2006. B. Shipley, Cause and Correlation in Biology: A User’s Guide to Path Analysis, Structural Equations and Causal Inference, Cambridge University Press, Cambridge, UK, 2000. Sarah > Given that you are dealing with diatoms across space (with environmental > measurements) and down time (in cores, often without environmental > measures), there may be an alternate approach possible based on calibration > approaches to inferred environments (e.g., WACAL) or modern analogs. I > would look at packages bio.infer, paltran, fossil, and analogue, and search > to see if anyone has pushed them in the direction you want to go. > > Tom > > > > On Thu, Mar 7, 2013 at 6:50 AM, Jay Kerns <gjkerns...@gmail.com> wrote: >> >> Dear Sarah, >> >> On Thu, Mar 7, 2013 at 9:32 AM, Sarah Goslee <sarah.gos...@gmail.com> >> wrote: >> > That sounds like a job for path analysis or for structural equation >> > modeling, depending on the level of sophistication desired and the >> > hypotheses to be tested. >> > >> >> *Yes!* I said almost the exact same thing (I didn't say anything >> about Path Analysis because I don't know much about it), but I had it >> in my mind that SEM was targeted more to sociological things and >> didn't know if/that it was common in ecological contexts. Anyway, >> it's nice to hear that word coming from somebody else. >> >> > There are plenty of good resources for both, in and out of R. >> >> Indeed. I have some work to do. Thank you. >> >> -- >> Jay >> >> -- Sarah Goslee http://www.functionaldiversity.org _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
