perhaps ... library("fortunes") fortune("surgery")
Cheers, Bert On Thu, Nov 18, 2010 at 1:57 PM, Ben Bolker <bbol...@gmail.com> wrote: > Alaios <alaios <at> yahoo.com> writes: > >> >> Hello everyone. >> I would like to find the sample covariance matrix using R. >> >> So far I read on the wikipedia what a sample_covariance is >> http://en.wikipedia.org/wiki/Sample_covariance >> >> according to wikipedia one vector is >> enough to calculate the sample covariance matrix. > > I'm sorry, where does it say that?? The expression given > for the sample covariance is > > q_{ij}=\frac{1}{N-1}\sum_{k=1}^{N} > \left( x_{ik}-\bar{x}_i \right) \left( x_{jk}-\bar{x}_j \right) . > > if N=1 this whole thing will go up in smoke: the denominator and > numerator will both be zero. > > >> In R I tried cov(myvector) and I get the reply that I need to >> pass either two argument or one matrix with x,y >> values . >> >> How can I find the sample covariance matrix? >> > > You need more than one sample (!); even trying to do it with > two samples would give you a mathematically well-defined but > statistically awful estimate. > > I strongly suggest that you consult a statistics book or > a local expert ... > > good luck > > ______________________________________________ > 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. > -- Bert Gunter Genentech Nonclinical Biostatistics ______________________________________________ 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.