Re: [R] meta-analysis in R

2007-06-21 Thread Mike Cheung
Dear Bernd, Please be careful in reading the example of meta-regression (12.4) in http://cran.r-project.org/doc/vignettes/HSAUR/Ch_meta_analysis.pdf. In that example, the variance component was estimated under a model without any covariate. Then the estimated variance component was used as the

Re: [R] Comparison of correlation coefficients

2006-09-18 Thread Mike Cheung
Dear Donglei Hu, If you have two correlation coefficients, you may try cordif {multilevel} and cordif.dep {multilevel} for the independent correlations and for the dependent correlations, respectively. However, they are both based on the sampling distribution of correlation coeficient. A better

[R] how to fix the level-1 variances in lme()?

2005-09-29 Thread Mike Cheung
Dear all, Edmond Ng (http://multilevel.ioe.ac.uk/softrev/reviewsplus.pdf) provides an example to fit the mixed effects meta-analysis in Splus 6.2. The syntax is: lme(fixed=d~wks, data=meta, random=~1|study, weights=varFixed(~Vofd), control=lmeControl(sigma=1)) where d is the effect size, study

[R] Getting empirical percentiles for data

2005-01-06 Thread Mike Cheung
Dear List, I have some discrete data and want to calculate the percentiles and the percentile ranks for each of the unique scores. I can calculate the percentiles with quantile(). I know that ecdf can be used to calculate the empirical cumulative distribution. However, I don't know how to