I'm fitting a lme growth curve model with two predictors and their interaction as predictors. The multilevel model is nested so that level 1 is time within the individual, and level 2 is the individual. I would like to plot the mean group-level trajectories at plus and minus 1 SD from the mean of the main effects composing the interaction term. Thus, the plot should have 4 lines (mean trajectories) representing all combinations of the two predictors (where LO = -1sd from its mean, and HI = +1sd from its mean): -LO predictor, LO moderator -LO predictor, HI moderator -HI predictor, LO moderator -HI predictor, HI moderator
They are growth curves, so the plot should have 'time' on the x-axis and 'outcome' on the y-axis. Here's a sample model: library(nlme) set.seed(123) dataset <- NULL dataset$id <- rep(1:100, each=10) dataset$time <- rep(1:10,100) dataset$outcome <- rnorm(1000, mean=100, sd=15) dataset$predictor <- rnorm(1000, mean=10, sd=3) dataset$moderator <- rnorm(1000, mean=5, sd=2) dataset <- as.data.frame(dataset) dataset[sample(1:1000, 400, replace=F),"outcome"] <- NA dataset[sample(1:1000, 400, replace=F),"predictor"] <- NA dataset[sample(1:1000, 400, replace=F),"moderator"] <- NA model <- lme(outcome~ time + predictor + moderator + predictor*moderator, random=~1 + time + predictor|id, data=dataset, na.action=na.omit) How can I plot the interaction on the mean group-level trajectories using ggplot? Thanks in advance! -- View this message in context: http://r.789695.n4.nabble.com/Plotting-interactions-from-lme-with-ggplot-tp4631454.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
