On Thu, 2010-11-25 at 22:56 +0000, Chris Mcowen wrote: > Hi, > > I am not sure if it is more robust than a discriminant function but it > is certainly capable if differentiating between species based on > morphology. I used 12 measurements in my fish.
PCA extracts linear combinations of the data that explain maximum variance in the data, subject to the constraint that the sets of linear combinations (the "axes") are uncorrelated (orthogonal). LDA extracts linear combinations of the data that best separate the group (species) means. LDA would seem to be doing a more direct analysis if the question is how can I differentiate my species in terms of their morphometrics. G > What did your PCA results show? > > Unfortunately I haven't got round to publishing my data yet but I can > send you a paper by my supervisor who did a similar analysis looking > at morphological differentiation in cichlids in Africa. > > Chris > > Sent from my iPhone > > On 25 Nov 2010, at 20:30, Mike Gibson <megalop...@hotmail.com> wrote: > > > Sorry for the delay in getting back to you. > > > > I did use a PCA. > > > > I wanted to run a discriminant function as a comparison. Is PCA more > > robust at detecting differences based on the morphometrics? > > > > Can you give me the details of your masters (title, school, ect) so I can > > reference it. > > > > Mike > > > > > CC: r-help@r-project.org > > > From: chrismco...@me.com > > > Subject: Re: [R] discriminant function analysis > > > Date: Tue, 16 Nov 2010 22:12:32 +0000 > > > To: megalop...@hotmail.com > > > > > > Hi, > > > > > > I did this exact thing for my masters, with intertidal fish, I just used > > > a PCA? have you tried that? > > > > > > Sent from my iPhone > > > > > > On 16 Nov 2010, at 17:01, Mike Gibson <megalop...@hotmail.com> wrote: > > > > > > > > > > > My objective is to look at differences in two species of fish from > > > > morphometric measurements. My morphometric measurements are head > > > > length, eye diameter, snout length, and measurements from tail to each > > > > fin. I want to use discrimanant function analyis to determine if there > > > > are differences between the two species. > > > > > > > > I am familiar with R but new to discrimannt function analysis. I want > > > > to learn how to run this analysis in R. My internet search has not been > > > > very successful. I did see refrence of the linear discriminant function > > > > (lda) in R but I am not sure if this is the correct function for me. > > > > > > > > Any advice and especially a reference to any examples would be greatly > > > > appreciated. > > > > > > > > Thanks. > > > > > > > > Mike > > > > [[alternative HTML version deleted]] > > > > > > > > ______________________________________________ > > > > R-help@r-project.org mailing list > > > > https://stat.ethz.ch/mailman/listinfo/r-help > > > > PLEASE do read the posting guide > > > > http://www.R-project.org/posting-guide.html > > > > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
