Hi all, Apologies if this is more a stats question than an R question but I do need help with R for the solution.
I'm calculating the degree of synchrony of population fluctuations through time in a community, based on Loreau & Mazencourt 2008 paper. Loreau, Michel, and Claire de Mazancourt. (2008) "Species synchrony and its drivers: Neutral and nonneutral community dynamics in fluctuating environments." The American Naturalist 172, no. 2: E48-66. doi:10.1086/589746. I am using this code: dat = cbind(sp1 = rnorm(100, 10, 2), sp2 = rnorm(100, 10, 2)) #Two species with random independent abundance sampled 100 times. V = var(dat) # variance-covariance matrix for all species # calculate synchrony index from covariance matrix synchrony = function(V) { d = sqrt(diag(V)) sum(V) /sum(d%*%t(d)) } S = synchrony(V) S runs from 0 (total Asynchrony) to 1 (total Synchrony) with 0.5 = random or no synchrony as described by the authors. I am wondering if there is a to calculate a threshold or value of S at which I can say that there is "significant Asynchrony in this community" or significant Synchrony in this community". For example is 0.3 asynchronous or not really ? Should this threshold based on the data range or the variation itself? In which case how would I code this calculation? Or should I just say that anything <0.25 is significantly/very Asynchronous? In which case how can I generate a column to say if S <0.25 its asynchronous or if its >0.75 its synchronous? Thanks for your feedback Tania Tania Bird MSc PhD Student, Geo Ecology Lab Ben Gurion University [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology