Marc, Basic R stats functions like prcomp have a predict method that can be used to "predict" (calculate) scores with 'newdata'. This is standard, and has been in R for ever. Most textbooks of multivariate analysis should handle this issue.
In community ecological context, see functions predict.cca and predict.rda in vegan. These take argument 'newdata' which can be new community data -- depending on what you want to predict (argument 'type'). Function calibrate.cca documented in the same help page can be used to predict values of constraining variables in constrained ordination (CCA, RDA) from community composition, also with 'newdata' communities. Cheers, Jari Oksanen ________________________________________ From: r-sig-ecology-boun...@r-project.org [r-sig-ecology-boun...@r-project.org] on behalf of Marc Taylor [marchtay...@gmail.com] Sent: 23 May 2012 10:19 To: r-sig-ecology@r-project.org Subject: [R-sig-eco] PCA as a predictive model Hello R-sig-ecology group, I was wondering if anyone is aware of an example where PCA is used as a predictive model? A community analysis example might be to predict the PC values of a sample given its community composition. I had thrown this question up on a statistics forum ( http://stats.stackexchange.com/questions/28916/can-empirical-orthogonal-function-eof-analysis-be-used-as-a-predictive-model) but have gotten hardly any response. I imagined that there are some folks here that would have some insight into this problem. Many thanks, Marc [[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
