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...imes shuts down due to overheating. I'm now thinking about buying a more powerful desktop PC or laptop. Can anybody advise me on the best configuration to run R as fast as possible? I will use this PC exclusively for R so any other factors are of limited importance. Thanks, Michael Michael Haenlein Assocaite Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

Michael Haenlein wrote Dear all, I would like to use predict.lm to obtain a set of predicted values based on a regression model I estimated. When I apply predict.lm to two vectors that have the same values, the predicted values will be identical. I know that my regression model is not...

...rnative model in which the coefficients for x1 and x2 are constraint to be equal and to compare the fit of such a constraint model with the one of an unconstraint one. But again I'm not sure how this can be done using coxph. Could anyone help me out on this please? Thanks, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...et (N=100,000 with 89 variables per subject). This dataset is stored in a 100.000 x 89 matrix where each row describes one individual and each column one variable. What is the easiest way of selecting a subset of let's say 1.000 individuals out of that whole matrix? Thanks, Michael Michael Haenlein Associate Professor of Marketing ESCP-EAP European School of Management Paris, France [[alternative HTML version deleted]]

...ed predict.coxph and predict.survreg as well as the document "A Package for Survival Analysis in S" written by Terry M. Therneau but I have to admit that I'm a bit lost here. Could anyone give me some advice on how this could be done? Thanks very much in advance, Michael Michael Haenlein Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...NetSim which seems to be in this spirit, but I cannot get it to work. Could anyone point me to an R library that I could check out? I do not care much about the specific algorithm used as long as it allows me to vary clustering and degree polarization in certain ranges. Thanks, Michael Michael Haenlein Professor of Marketing ESCP Europe, Paris [[alternative HTML version deleted]]

...estimate the probability that a person is for example 16 years old. Is there some automatic way in R through which this can be done? I tried a Kernel density estimation of the histogram but this does not seem to provide what I'm looking for. Thanks very much for your help, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...strength. So my dataset looks like: Jim; Bob; 0.5 This measure of relationship strength can be interpreted like a distance measure in a spatial model. I assume that I need to work with the nb2listw function, but I am lost what to do in detail. Thanks very much for your help in advance! Michael Haenlein Assistant Professor of Marketing ESCP-EAP European School of Management Paris, France [[alternative HTML version deleted]]

...o determine the effect size for a regression coefficient in a multiple regression model? I have a model of the form lm(y ~ A*B*C*D) and would like to determine Cohen's f2 (http://en.wikipedia.org/wiki/Effect_size) for each predictor without having to do it manually. Thanks, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...evidently does not make sense: y <- rnorm(9) model <- lm (y ~ x1 + x2 + x1*x2) summary(model) Is there some function within R or in some separate library that allows me to estimate such a regression without obtaining inconsistent results? Thanks for your help in advance, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...x_new should be equal to x for the top n categories (i.e. the top n levels with the highest occurrence) and NAN elsewhere. For example, for n=3 x_new would have three levels: The three most common levels of x + NAN. Is there some convenient way of doing this? Thanks in advance, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...able in Equation 2. Additionally some independent variables that appear in Equation 1 are also included in Equation 2. I assume that I cannot estimate these two regressions separately using lm. Is there an efficient way to estimate these equations? Thanks very much in advance, Michael Michael Haenlein Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

.... I think for an experienced programmer the job should not take more than 2-3 days (probably less), but this is to be decided once the person has looked at the code. In case you are interested, please send me a brief message so that I can provide you with more details, Thanks, Michael Michael Haenlein Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

Dear all, I have some trouble understanding the chisq.test function. Take the following example: set.seed(1) A <- cut(runif(100),c(0.0, 0.35, 0.50, 0.65, 1.00), labels=FALSE) B <- cut(runif(100),c(0.0, 0.25, 0.40, 0.75, 1.00), labels=FALSE) C <- cut(runif(100),c(0.0, 0.25, 0.50, 0.80, 1.00), labels=FALSE) x <- table(A,B) y <- table(A,C) When I calculate the test statistic by hand

...uestions: First, can survreg handle time-dependent covariates? The description for this function does not make reference to them. And second, in case survreg cannot deal with time-dependent covariates, is there a similar function in some other package that can? Thanks very much, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

...he size of each group. So group 1 can contain 2 items, group 2 3 items, group 4 4 items, etc. I think this is probably something that could be done with constrOptim() but I'm not exactly sure how. Any help is very much appreciated! Thanks very much in advance, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France [[alternative HTML version deleted]]

Dear all, I am running a simulation in which I randomly generate a series of vectors to test whether they fulfill a certain condition. In most cases, there is no problem. But from time to time, the (randomly) generated vectors are too large for my system and I get the error message: "Cannot allocate vector of size x". The problem is that in those cases my simulation stops and I have to

...d have positive signs. I don't really understand this. Do I have to add up the coefficient for the main effect and the ones of all interaction effects to get a total effect of a on y? Or am I doing something wrong here? Thanks very much for your answer in advance, Regards, Michael Michael Haenlein Associate Professor of Marketing ESCP Europe Paris, France Call: lm(formula = y ~ a * b * c * d) Residuals: Min 1Q Median 3Q Max -44.919 -5.184 0.294 5.232 115.984 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 27.3067 0.8181 33.379...

Dear all, This is probably more related to statistics than to [R] but I hope someone can give me an idea how to solve it nevertheless: Assume I have a variable y that is a function of x: y=f(x). I know the average value of y for different intervals of x. For example, I know that in the interval[0;x1] the average y is y1, in the interval [x1;x2] the average y is y2 and so forth. I would like to

Dear all, I'm using a while loop in the context of an iterative optimization procedure. Within my while loop I have a counter variable that helps me to determine how long the loop has been running. Before the loop I initialize it as counter <- 0 and the last condition within my loop is counter <- counter + 1. I'd like to print out the current status of "counter" while the