[R] Help with slope comparisons

Hello Forum, I have data for two groups of subjects for a ratio variable (cortisol level) assessed three times during the day (at 0600, 0900 and 2100 hours). So I have three means for each group. I have been asked to do a slope analysis to compare the two groups. According to my

[R] Question about factor that is numeric, in aov()

answers. But aov(score~group, data=mydata) also produces an ANOVA table, with incorrect entries. My question is: what exactly is R doing when I did not specify that group was a factor? Ravi Kulkarni -- View this message in context: http://r.789695.n4.nabble.com/Question-about-factor

Re: [R] U de Theil

I do not know if this is what you want, but take a look at the External links at the bottom of the Wikipedia page: http://en.wikipedia.org/wiki/Theil_index Ravi -- View this message in context: http://r.789695.n4.nabble.com/U-de-Theil-tp2164441p2164458.html Sent from the R help mailing

[R] Shapiro-Wilk for levels of factor

Hello, I have data for an ANOVA where the between-subjects factor has three levels. How do I run a test of normality (using shapiro.test) on each of the levels of the factor for the dependent variable separately without creating extra datasets? Thanks, Ravi

Re: [R] Shapiro-Wilk for levels of factor

Thanks! Exactly what I wanted. Ravi -- View this message in context: http://n4.nabble.com/Shapiro-Wilk-for-levels-of-factor-tp1555254p1555720.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list

[R] Difference in Levene's test between R and SPSS

Hello, I notice that when I do Levene's test to test equality of variances across levels of a factor, I get different answers in R and SPSS 16. e.g.: For the chickwts data, in R, levene.test(weight, feed) gives F=0.7493, p=0.5896. SPSS 16 gives F=0.987, p=0.432 Why this difference? Which

Re: [R] Difference in Levene's test between R and SPSS

I think I have an answer: SPSS uses absolute deviations from the _mean_ in Levene's test. (See calculation in http://www.uvm.edu/~dhowell/gradstat/psych340/Lectures/Anova/anova2.html) R uses absolute deviations from the _median_ (R help). So the difference. Ravi -- View this message in

Re: [R] Difference in Levene's test between R and SPSS

I forgot to reply to Peter Ehler's question: I am using Levene's test in the car package. Ravi -- View this message in context: http://n4.nabble.com/Difference-in-Levene-s-test-between-R-and-SPSS-tp1555725p1556016.html Sent from the R help mailing list archive at Nabble.com.

[R] lattice package: Changing colors in graphs

Giving different colors to plots of different levels of a factor can be pleasing. For a boxplot, for example, the following produces a nice plot: boxplot(len~supp*dose, data=ToothGrowth, col=c(“orange”,”gray”)) If I try to specify (using the lattice package) histogram(~len|supp*factor(dose),

[R] Type-I v/s Type-III Sum-Of-Squares in ANOVA

Hello, I believe the aov() function in R uses a Type-I sum-of-squares by default as against Type-III. This is relevant for me because I am trying to understand ANOVA in R using my knowledge of ANOVA in SPSS. I can only reproduce the results of an ANOVA done using R through SPSS if I specify

Re: [R] Type-I v/s Type-III Sum-Of-Squares in ANOVA

Apologies. I should have checked the archives first... I did not know that it was so widely discussed... Ravi -- View this message in context: http://n4.nabble.com/Type-I-v-s-Type-III-Sum-Of-Squares-in-ANOVA-tp1573657p1573734.html Sent from the R help mailing list archive at Nabble.com.

[R] ANOVA Types and Regression models: the same?

of ANOVA correspond to? I mean that I think of my ANOVA as a regression model (a General Linear Model) and the various ways of entering predictors as the various ANOVA Types. Hope that makes sense... Ravi Kulkarni -- View this message in context: http://n4.nabble.com/ANOVA-Types-and-Regression

Re: [R] Type-I v/s Type-III Sum-Of-Squares in ANOVA

Hello, Since I initiated this discussion some days ago, I discovered a paper that may be of interest: ANOVA for unbalanced data: Use Type II instead of Type III sums of squares by ØYVIND LANGSRUD Statistics and Computing 13: 163–167, 2003 Ravi

Re: [R] Help! I turned my data into junk!

It's probably binary data - which implies that you can only read it with the application that created it. What is the filename extension? Ravi -- View this message in context: http://n4.nabble.com/Help-I-turned-my-data-into-junk-tp1585481p1585585.html Sent from the R help mailing list archive

[R] Source code for the t-distribution

I have tried looking for the source code for the pt() function in https://svn.r-project.org/R/trunk/src/library/stats/ and am unable to find it there. Can someone please tell me where to find it? Thanks, Ravi Kulkarni -- View this message in context: http://n4.nabble.com/Source-code

Re: [R] Help with ANOVA in R

for explicit examples of ANOVA in R: http://www.personality-project.org/R/r.anova.html Ravi Kulkarni -- View this message in context: http://n4.nabble.com/Help-with-ANOVA-in-R-tp1585992p1586936.html Sent from the R help mailing list archive at Nabble.com. __ R

[R] Coding of categorical variables for logistic regression?

for the categorical variables as required by some statistical software packages, with some sort of numeric dummy-variable coding? I am using: glm(binvar~x+y+z, family=binomial(link=logit)) Thanks, Ravi Kulkarni -- View this message in context: http://n4.nabble.com/Coding

Re: [R] Coding of categorical variables for logistic regression?

How do I use the extra information that two of my predictors are ordinal? (I did not know I could do that.) Thanks, Ravi -- View this message in context: http://n4.nabble.com/Coding-of-categorical-variables-for-logistic-regression-tp1694250p1694644.html Sent from the R help mailing list

[R] Problem comparing logistic regression output with SPSS.

in the model? Is that what is causing the difference? Thanks, Ravi Kulkarni -- View this message in context: http://n4.nabble.com/Problem-comparing-logistic-regression-output-with-SPSS-tp1694767p1694767.html Sent from the R help mailing list archive at Nabble.com

[R] Boundary kernel for kernel density plot?

. Thanks, Ravi Kulkarni -- View this message in context: http://n4.nabble.com/Boundary-kernel-for-kernel-density-plot-tp1746968p1746968.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https

Re: [R] reading excel into R

Use R Commander to do this. R Commander is a R package that offers a GUI for R. It can be downloaded like any other R package. If you use R Commander, there is a menu option where you specify that you want to read an Excel file (you can also read text, SPSS, Minitab, Stata, Access... files). It

Re: [R] roccomp

The ROCR package has methods to compute AUC and related methods. You might want to check it out. Ravi -- View this message in context: http://n4.nabble.com/roccomp-tp1748818p1748903.html Sent from the R help mailing list archive at Nabble.com. __

Re: [R] roccomp

Yes, there does not seem to be a method for comparing two ROC curves in ROCR. But I found a discussion in the R-archives which may be useful: http://tolstoy.newcastle.edu.au/R/help/06/03/23667.html You should also see the replies to that post. I am also interested in

[R] Scope of variable?

I know this is a very elementary question... I could not find a solution looking at old posts. I am unable to access a variable outside the scope of a for loop, even when the variable was defined before the loop: haar - function() { a = c(1.4560773, 2.3752412, 0.9798882, 3.0909252, 2.3986487,

Re: [R] Scope of variable?

Of course! Works fine now. Thanks, Martyn and Jim... Ravi -- View this message in context: http://r.789695.n4.nabble.com/Scope-of-variable-tp3381485p3381932.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing

[R] Time series example in Koop

I am trying to reproduce the output of a time series example in Koop's book Analysis of Financial Data. Koop does the example in Excel and I used the ts function followed by the lm function. I am unable to get the exact coefficients that Koop gives - my coefficients are slightly different. After

[R] Bootstrapped Tobit regression - get standard error 0...

I am trying to work out a bootstrapped Tobit regression model. I get the coefficients all right, but they all have standard error zero. And I am unable to figure out why. I know the coefficients are correct because that's what I get when do a Tobit (without bootstrapping). Here's my code: #

Re: [R] how can i get AIC value for AR model

If you look at the documentation for ar, you will find the following description of aic: aic The differences in AIC between each model and the best-fitting model So this means that your model order is 5 (look at the pacf). If you want the actual AIC of your model: (I call your

[R] Structural equation modelling in R compared with Amos

Can anyone give me links to reviews/comparisons of R with Amos for SEM? I have found some but they are a little old (2009). Ravi -- View this message in context: http://r.789695.n4.nabble.com/Structural-equation-modelling-in-R-compared-with-Amos-tp3921654p3921654.html Sent from the R help

[R] Bug in options(digits=n)??

This is in version 2.10.1 sqrt(3) [1] 1.732051 6/7 [1] 0.8571429 options(digits=3) sqrt(3) [1] 1.73 6/7 [1] 0.857 sqrt(7) [1] 2.65 7/9 [1] 0.778 Ravi -- View this message in context: http://r.789695.n4.nabble.com/Bug-in-options-digits-n-tp4082537p4082537.html Sent from the R help

[R] References for book R In Action by Kabacoff

I know this is not really an R question - it is a query about a recent book on R (R In Action) by Robert Kabacoff, (Manning Publications 2011). There are many references to interesting topics in R in the book, BUT, I do not find a bibliography/list of references in the book! Does anybody know if

[R] Error using qda on the spambase training dataset

Hello, I am trying to run the code for quadratic discriminant analysis with the Spambase data set following the code example in the book R in a Nutshell by Joseph Adler (page 443). The line of code: spam.qda - qda(formula=is_spam~., data=spambase.training)