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Dear Rdevelopers The background for this email is that I was helping a PhD student to improve the speed of her R code. I suggested to replace calls like t(AA)%*% BB by crossprod(AA,BB) since I expected this to be faster. The surprising result to me was that this change actually made her code slower. > ## Examples : > > AA <- matrix(rnorm(3000*1000),3000,1000) > BB <-

Dear list, first apologies for this is not strictly an R question but a theoretical one. I have read that use of k-means clustering assumes sphericity of data distribution. Can anyone explain me what this means? My statistical background is too poor. Is it another kind of distribution, like gaussian or binomial? What does it happen if the distribution is not spherical? Could you give me an

Hi Elaine I do not use it very often. I programmed it to mimic Minitab functions (partly) with some adons from czech statistics textbook written by M.Meloun (meloun militky statistics - first hit in google) Basically you can have your data in some data frame or they can be as separated vectors. The function itself expects input of 3 vectors, but you can easily to modify it for imput as