Dear Etienne, I agree. Pedro Peres-Neto kindly wrote to confirm that there is a typo in equation 9. He also pointed out that the Matlab code in supplement 2 of the paper is correct. Best, Ivan
________________________________ From: Etienne Laliberte [mailto:etiennelalibe...@gmail.com] Sent: Thu 4/7/2011 6:47 PM To: Ivan Jimenez; r-sig-ecology@r-project.org Subject: RE: [R-sig-eco] equation 9 Peres-Neto et al. 2006 Dear Ivan, In such situations, it's probably best to contact the corresponding author first. Etienne -----Original Message----- From: r-sig-ecology-boun...@r-project.org [mailto:r-sig-ecology-boun...@r-project.org] On Behalf Of Ivan Jimenez Sent: Friday, 8 April 2011 4:19 AM To: r-sig-ecology@r-project.org Subject: [R-sig-eco] equation 9 Peres-Neto et al. 2006 Dear r-sig-eco members, I am applying the bootstrap procedure to test differences between fractions from RDA variation partitioning, following the interesting a very useful paper by Peres-Neto et al. (2006, Variation partitioning of species data matrices: estimation and comparison of fractions. Ecology 87: 2614-2625). I don't have (and don't use) Matlab, so I am implementing the test in R, which would seem straightforward to do given the functions available in package vegan. Nonetheless, I would like confirmation that there is a typo in equation 9 (page 2621) of the Peres-Neto et al. paper. The Matlab code in supplement 2 of the paper (file "TestingFractionDiffRDA.m", deposited here: http://www.esapubs.org/archive/ecol/E087/158/suppl-2.htm) would seem right, but it would seem not to match equation 9 in the paper. In particular, equation 9, in page in 2621, is written this way: Yhat_xboot = X Bx (I-P) Y_xboot Yhat_wboot = W Bw (I-P) Y_wboot Where (following the notation of the paper): Bx = ( (X'X)^-1) X' (I-P) Y Bw = ( (W'W)^-1) W' (I-P) Y I suspect equation 9 should be: Yhat_xboot = X ( (X'X)^-1) X' (I-P) Y_xboot Yhat_wboot = W ( (W'W)^-1) W' (I-P) Y_wboot I would appreciate it if someone has the time to look at this and either confirm or correct my observation. Best regards, Ivan Jimenez [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
