search for: jlvw

Dear UseRs I would like to show my students how to use "resampling" to solve the following simple problem: If a family has two children of which one is a boy, what is the probability that the other child is also a boy. The answer is (obviously) 1/3, and can be show easily using the usual methods. But I would like to get the students to think of resampling, by doing the following:

>>>>> "Jacob" == Jacob van Wyk <jlvw at rau.ac.za> writes: Jacob> Could anybody please help: I simply want to generate Jacob> random samples from a multinomial distribution with Jacob> fixed n and given probability vector p. Jacob> How can I do this? I've recently written the following {for the R...

Hello again, I'm getting close to a working setup but still run into glitches here and there. I have 2 Ubuntu servers working as AD server, one Ubuntu desktop with winbind configured. I've setup a number of accounts with Unix properties. I've been primarily testing with my own account which works just fine. I've now assigned Unix properties to another account. When I run

Hallo Could anybody please help. I have a simple linear regression model with 5 predictors. I want to use "bootstrap residuals" to make inferences regarding beta(2)hat. After fitting the model y=b0+b1+b2+b3+b4+b5 I tried the following: mod <- lm(y ~ x1+x2+x3+x4+x5) res <- resid(mod) pred <- predict(mod) Now, I have tried boot(res, lm(res+pred ~ x1+x2+x3+x4+x5)$coef[3],

I have a question regarding the package LOCFIT of C Loader. After fitting a smooth surface (y modeled by two regressors), I can't seem to find a nice way of making a perspective (or other 3d plot). The contours don't look quite so good. It is meant to be used as illustration of smoothing to my students in regression analysis. Could anybody perhaps assist me in producing a

Hi I run R in Windows. Is there a simple way of changing the prompt symbol ">" to, say, "R>" ? (Not just for a temporary session, but every time R command window is opened.) The documentation of doing this is rather "sparse". Much appreciated for your assistance. Jacob Jacob L van Wyk Department of Statistics University of Johannesburg, APK P O Box 524

Hallo I am trying to use the package LocFit to follow the example given in an Introductory note of C Loader concerning density estimation. It involves the "geyser" dataset (107 observations on durations, inlc in the package). I have tried the following (using the latest version of R): fit.of <- locfit(~geyser,flim=c(1,6),alpha=c(0.15,0.9)) plot(fit.of,get.data=T,mpv=200) This

This might be a trivial question, but I would appreciate if anybody could suggest an elegant way of plotting a function such as the following (a simple distribution function): F(x) = 0 if x<=0 =(x^2)/2 if 0<x<=1 =2x-((x^2)/2)-1 if 1<x<=2 =1 if x>2 This is just an example. In this case it is a continuous function. But how to do it in general in an elegant way.

Hallo Is there an elegant way to do the following: Dataset consists of 2 variables: var1: some measurements, and var2: a grouping variable with two values, 1 and 2. There are (say) 10 measurements from group 1 and 15 measurements from group 2. The idea is to study the permutation distribution of mean(group 1) * mean(group2). One way would be to permute 1s and 2s and select the corresponding

Sorry for the repeat. The PRESS statistic is defined as sum(y-yhat(i))^2, where yhat(i) denotes the ith predicted value using all the data except the ith case (as used typically in linear models). Thanks again Jacob Jacob L van Wyk Department of Mathematics and Statistics Rand Afrikaans University P O Box 524 Auckland Park 2006 South Africa Tel: +27-11-489-3080 Fax: +27-11-489-2832

I hope somebody can help. A student of mine is doing a study on Measurement Error models (errors-in-variables, total least squares, etc.). I have an old reference to a "multi archive" that contains leiv3: Programs for best line fitting with errors in both coordinates. (The date is October 1989, by B.D. Ripley et al.) I have done a search for something similar in R withour success. Has