similar to: Simple simulation in R

dear list I am student M.S. statistics in department statistics . I am working in the function "nls" in the [R 2.3.1] with 246 data and want to fit the "exp" model to vectors( v and u ) but I have a problem to use it u 5.000000e-13 2.179057e+03 6.537171e+03 1.089529e+04 1.525340e+04 1.961151e+04 2.396963e+04 2.832774e+04 3.268586e+04 3.704397e+04 4.140209e+04

Hello everyone, I am looking at the joint spatial distribution of 2 kinds of organisms (estimated on a grid of points) and want to test for significant association or dissociation. My first question is: do you know a nice technique to do that, considering that I have a limited number of points (36) but that they are repeated (4 times)? I did GLMs to test for correlations between the

Does anyone know of research on the effects of rounding on regression? e.g., when you ask people "How often have you _______?" you are more likely to get answers like 100, 200, etc. than 98, 203, etc. I'm interested in investigating this, but don't want to reinvent the wheel. thanks Peter Peter L. Flom, PhD Assistant Director, Statistics and Data Analysis Core Center for

Hello I am running R 1.8.1 on a Windows platform I am attempting to fit an ordinal logistic regression model, using the polr function, as described in Venables and Ripley. But when I try model4 <- polr(ypsxcat~committed + as.factor(sex) + as.factor(drugusey) + anycsw + as.factor(sex)*committed + as.factor(sex)*as.factor(drugusey)+as.factor(sex)*anycsw, data = duhray) I get a message

Hello Using R 2.2.1 on a Windows machine. Has anyone programmed the Welch test for equality of variances? I tried RSiteSearch, but this gave references to t test and oneway.test, which are not quite what I need.....I need the Welch test itself, for use in a meta-analysis (to determine if variances are equal). TIA Peter Peter L. Flom, PhD Assistant Director, Statistics and Data Analysis

Thanks for all the help on my earlier questions..... How do you plot a simple time series with unequal intervals? I have the following dateofpoll <- as.ts(c("6/1/02", "7/1/02", "10/1/02", "1/4/03", "1/25/03", "6/7/03", "7/16/03", "8/17/03", "9/4/03")) reelect <- c(51, 47, 49, 51, 49, 49, 46, 45, 40)

Pursing my earlier question, when I tried loading Lindsey's gnlm, I got a message Loading required package: rmutil Warning message: There is no package called 'rmutil' in: library(package, character.only = TRUE, logical = TRUE, warn.conflicts = warn.conflicts, According to the R documentation http://finzi.psych.upenn.edu/R/doc/html/packages.html rmutil is in the standard

Sorry to keep asking elementary questions......I appreciate the help. I am trying to create a dotchart with the rows sorted according to the values, rather than the labels. When I try prof <- c('Accountant', 'Administrative assistant', 'Garment worker', 'Cook', 'Dentist', 'General practictioner', 'Graduate student', 'High level

Running R 1.8.1 on a Windows machine In dotchart, I would like to shrink the labels on the tick marks (that is, the numbers) without shrinking anything else. I could not find this in either the Rhelp archives or in ?dotchart, which recmmends cex to avoid 'label overlap', but cex shrinks all the characters in the plot. Is there a way to do this? Thanks Peter Peter L. Flom, PhD

Has anyone programmed condition indexes in R? I know that there is a function for variance inflation factors available in the car package; however, Belsley (1991) Conditioning Diagnostics (Wiley) notes that there are several weaknesses of VIFs: e.g. 1) High VIFs are sufficient but not necessary conditions for collinearity 2) VIFs don't diagnose the number of collinearities and 3) No one has

Hello I am running R 2.0.1 on Windows, I am attempting to use Frank Harrell's 'fastbw' function (from the Design library), but I get an error that the fit was not created with a Design library fitting function; yet when I go to the help for fastbw (and also look in Frank's book Regression Modeling Strategies) it appears that fastbw should work with a model created with lm.....

Hello again I am trying to fit an ordinal logistic model using the polr function from MASS. When I run model.loan.ordinal <- polr(loancat~age + sex + racgp + yrseduc + needlchg + gallery + sniffball + smokeball + sniffher + smokeher + nicocaine + inject + poly(year.of.int,3) + druginj + inj.years) I get an error Error in optim(start, fmin, gmin, method = "BFGS", hessian =

I have found that specifying different "sizes" in the sample command has a funny effect on the random sampling. The code below is a condensed version of a function I wrote to simulate a bootstrap method. For simplicity, I eliminated the internal bootstrap loop, but kept a statement to draw one bootstrap sample, because this is where the problem occurs. The output (mean(y)^2) should be

I was under the impression that the tree method (e.g. as implemented in rpart) was insensitive to monotonic transformations of the dependent variable. e.g. Breiman Olshen et al. Classification and Regression Trees state "In a standard data structure [a tree] is invariant under all monotone transformations of individual ordered varaibles" (p. 57) However, I get very different results

I'd like to thank John Fox and Chuck Cleland for their help in resovling this issue. It turned out to be something simple, but perhaps others have had similar problems In my original data frame, I had 4 categories of race/ethnicity. One of the categories (other) was very small, and not similar to any of the other three categories, so I created a new data frame deleting those people.

I have a dataframe called cvar, with two variables (among many others) called MSA and ACTUP. Both are numeric. This was working fine. Then I found out that for two MSAs, ACTUP should be 1, not 0. so I tried cvar$ACTUP[cvar$MSA == 6840] <- 1 cvar$ACTUP[cvar$MSA == 5360] <- 1 but when I try table(cvar$MSA, cvar$ACTUP) the level of ACTUP for those two MSAs has not changed, and is still

Hello I have a dataframe that looks like this MSA CITY HIVEST YEAR YR CAT 1 0200 Albuquerque 0.50 1996 1996 5 2 0520 Atlanta 13.00 1997 1997 5 3 0720 Baltimore 29.10 1994 1994 1 4 0720 Baltimore 13.00 1995 1995 5 5 0720 Baltimore 3.68

When I try citypro <- sas.get('c:/ndri/cvar/data', member = 'citypro2') I get the following errors and warnings: 'sas' is not recognized as an internal or external command, operable program or batch file. 'less' is not recognized as an internal or external command, operable program or batch file. Error in sas.get("c:/ndri/cvar/data", member =

Hello again I have modeled a tree using rpart, with the DV being a log transformation of the variable I am really interested in (I transformed the DV due to extreme skewness). By default, text.rpart labels the nodes with the value of yval, which in this case is not what I want; I'd like the labels to be on the original metric, but label in text.rpart requires a "column name of

First, my apologies for not giving all the details in my first post. Second, the problem was somewhat more complicated than simply using help.search('polr') or library(MASS). When I tried these, I got notices that polr could not be found anywhere, and that no package called MASS existed. When I went to the CRAN site, there was no package called MASS. I am not sure how I installed R