Dear Phil, Yes, that's a bit clearer. One can invent data configurations where certain studentized residuals are undefined. For example, try the following:
y <- c(0, 0, 0, 0, 0, 1) x <- 1:6 xx <- (1:6 - 3.5)^2 rstudent(lm(y ~ x)) rstudent(lm(y ~ xx)) plot(x, y) plot(xx, y) The plots should clarify what's going on. I'm copying to r-help since the discussion began there. I hope this helps, John On Fri, 17 Oct 2014 18:35:59 +0200 Philip Stevens <chobop...@gmail.com> wrote: > Dear John, > > Thank you for your fast reply. Unfortunately I am out of office right now > but I will get back to you on Monday asap with a toy example and some code. > Meanwhile let me try to explain further. > > Basically not the glm but the outlierTest afterwards fails. And it only > fails if all values, used to set up the glm, are exactly 1 except for one > value which can be arbitrary large. I construct the glm from a vector of > doubles (the target values) and a vector of other numeric values(metadata). > (So this should be fit <- glm(targetVector ~ metadata) ) And want to check > if one of those doubles(in the target vector) is an outlier using > outlierTest(fit). The residuals are calculated by the glm but the > outlierTest does not report a p nor a q value for the one value in the > target vector which is not 1. And I can't figure out why... > > I hope this makes it a bit clearer. > Anyways I will come back to you on Monday. > > Best, > > Phil > Am 17.10.2014 17:43 schrieb "John Fox" <j...@mcmaster.ca>: > > > Dear Phil, > > > > After reading your posting several times, I still don't understand what > > you did. As usual, having a reproducible example illustrating the error > > would be a great help. I do have a guess about the source of the error: > > glm() failed in some way for the problematic case. > > > > Best, > > John > > > > ------------------------------------------------ > > John Fox, Professor > > McMaster University > > Hamilton, Ontario, Canada > > http://socserv.mcmaster.ca/jfox/ > > > > > > On Fri, 17 Oct 2014 12:53:30 +0200 > > Phil <chobop...@gmail.com> wrote: > > > Hi guys, > > > > > > I came across a strange phenomena and can't figure out why it happens by > > myself so here we go. > > > > > > I got a dataframe which consists of double numbers which I want to > > check, row-wise if there are outliers in the rows. > > > > > > So I iterate over the rows and create a glm using the numbers of that > > particular row. Which might look like this: > > > > > > case1) > > > x1 x2 x3 x4 x5 x6 x7 > > > x8 x9 x10 x11 > > > 0.00 3.91 0.00 0.00 0.00 68.03 40.39 0.00 > > > 0.00 0.00 4.11 > > > > > > or like this: > > > case2) > > > x1 x2 x3 x4 x5 x6 x7 > > > x8 x9 x10 x11 > > > 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 > > > 1.00 1.00 5.34 > > > > > > or any other combination of double numbers... > > > > > > however, using a glm like this: > > > > > > glModel <- glm(vector ~ some_other_meta_data_which_is_double_numbers) > > > > > > and testing it with: > > > > > > test.Res <- outlierTest(glModel,digits=4,cutoff=Inf,n.max=Inf) > > > > > > I always get a result consisting of the desired p and q values but not > > if the vector I use looks like case2. There is no error message and the > > computation does not stop either. > > > However, all p and q values are produced except for the last value x11. > > > > > > Any idea why this particular value gets dropped from the output of the > > outlierTest Method in the car package. > > > > > > Here is the sessioninfo: > > > > > > sessionInfo() > > > R version 3.1.1 (2014-07-10) > > > Platform: x86_64-redhat-linux-gnu (64-bit) > > > > > > locale: > > > [1] LC_CTYPE=en_US.utf8 LC_NUMERIC=C > > > [3] LC_TIME=en_US.utf8 LC_COLLATE=en_US.utf8 > > > [5] LC_MONETARY=en_US.utf8 LC_MESSAGES=en_US.utf8 > > > [7] LC_PAPER=en_US.utf8 LC_NAME=C > > > [9] LC_ADDRESS=C LC_TELEPHONE=C > > > [11] LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C > > > > > > attached base packages: > > > [1] stats graphics grDevices utils datasets methods base > > > > > > other attached packages: > > > [1] ggplot2_1.0.0 car_2.0-21 RColorBrewer_1.0-5 iNEXT_1.0 > > > [5] vegan_2.0-10 lattice_0.20-29 permute_0.8-3 > > > > > > loaded via a namespace (and not attached): > > > [1] colorspace_1.2-4 compiler_3.1.1 digest_0.6.4 grid_3.1.1 > > > [5] gtable_0.1.2 labeling_0.3 MASS_7.3-33 munsell_0.4.2 > > > [9] nnet_7.3-8 plyr_1.8.1 proto_0.3-10 Rcpp_0.11.2 > > > [13] reshape2_1.4 scales_0.2.4 stringr_0.6.2 tools_3.1.1 > > > > > > Any help is highly appreciated. > > > > > > Thanks > > > > > > Phil > > > > > > ______________________________________________ > > > 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. > > > > > > > > > > ------------------------------------------------ John Fox, Professor McMaster University Hamilton, Ontario, Canada http://socserv.mcmaster.ca/jfox/ ______________________________________________ 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.
