Andy, That’s correct: if you have coded your variable as a single factor, R (and hence vegan) will automatically create dummy variables. If you have originally coded your variable as a set of dummy variables, and you have done that correctly, you will get the same result. If you do not drop one of the dummy variables, R will do it for you and tell that some of your original variables were aliased. This will not influence the results, though.
In conclusion: everything goes, but it is best to use the R way and define your factor as a single factor. Cheers, Jari Oksanen > On 7 Feb 2017, at 10:48 am, Andrew Halford <andrew.half...@gmail.com> wrote: > > Hi Listers, > > I am running a partial RDA analysis and I have an environmental dataset > which includes a non-ordered factor representing reef type. > > I want to test for a significant linear trend in the environmental dataset > as part of the process of testing for spatial autocorrelation. > > e.g. lineartest <- anova(rda(env,latlong)) > > I have coded this Factor variable up as a group of dummy variables equal to > the number of different reef types to run the test but I am unsure if I > need to drop one of the dummy variables before running the linear test? > > I will revert back to a single Factor variable when I run the RDA as told > in the vegan documentation? > > My reading tells me that the call to RDA in Vegan will automatically deal > with creating dummy variables from a Factor variable presented in the model > but this is not the case > > cheers > > Andy > > > Andrew Halford Ph.D > Research Scientist (Kimberley Marine Parks) > Dept. Parks and Wildlife > Western Australia > > Ph: +61 8 9219 9795 > Mobile: +61 (0) 468 419 473 > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology