[R] fit.mult.impute() in Hmisc

2011-03-31 Thread Yuelin Li
I tried multiple imputation with aregImpute() and fit.mult.impute() in Hmisc 3.8-3 (June 2010) and R-2.12.1. The warning message below suggests that summary(f) of fit.mult.impute() would only use the last imputed data set. Thus, the whole imputation process is ignored. Not using a Design

[R] power for repeated-measures ANOVA lacking sphericity

2011-03-10 Thread Yuelin Li
). library(pwr) does not seem to support either. Many thanks in advance, Yuelin Li. = Please note that this e-mail and any files transmitted with it may be privileged, confidential, and protected from

[R] R2WinBUGS: Error in bugs(program=openbugs) but not openbugs()

2010-11-11 Thread Yuelin Li
I get an error when I call bugs(..., program=OpenBUGS, bugs.directory=c:/Program Files/OpenBUGS/OpenBUGS312), expecting, as suggested in help(bugs), that it would fit the model with openbugs() via BRugs. help(bugs) ... either winbugs/WinBUGS or openbugs/OpenBUGS, the latter makes use of

[R] plotcp() in rpart()

2008-05-30 Thread Yuelin Li
I have a general question about how to interpret the plotcp() graph. The cross-validation xerror value typically follows a decreasing pattern, from approximately 1.0 at the root node, then it crosses the 1SE boundary, reaches a plateau, and decreases further when the tree gets very complex

Re: [R] plotcp() in rpart()

2008-05-30 Thread Yuelin Li
What happens if plotcp() shows an V-shape profile? It seems that the predictors (I have a few) do not help the splits. Would it be reasonable to prune it at size 6? Or perhaps rpart() is not suitable for this analysis? What I meant on the last sentence was perhaps I made a

Re: [R] for loop in nls function

2008-04-29 Thread Yuelin Li
results[i]- nls(Tw ~ mu + ((alpha - mu)/(1 + exp(gamma*(B - Mean_Air, data = dem16, start = list(mu = 0.0001, alpha = 21.8, gamma = 0.22, B = 12.8)) } If you have a variable that codes site then you can try something like this to get the parameters over sites.

Re: [R] post hoc statistical power

2008-04-08 Thread Yuelin Li
Many thanks to John Fox and Charles C. Berry. Both point to the paper by Hoenig and Heisey (email from John Fox below): Another paper critical of post-hoc power calculations is Hoenig and Heisey, 2001. The Abuse of Power: The Pervasive Fallacy of Power Calculations for Data Analysis. The

Re: [R] Why can repeated measures anova with within between subjects design not be done if group sizes are unbalanced?

2007-11-08 Thread Yuelin Li
Hope I am not too late joining this thread. I believe the difference between R and SPSS is because SPSS adjusts the Type III SS by the harmonic mean of the unbalanced cell sizes. This calculation is discussed in Maxwell and Delaney (1990, pp. 271-297). In short, the best explanation I can offer