Dear All, Top panel of Figure 3 of this open access paper (see **link below**) shows 3 clusters of datapoints, each with five datapoints. The authors note:
"The dotted line represents the regression of well-being (y) on workload
(x) within each cluster (i.e., the pooled within-cluster regression, Beta_w)". Say I have the hypothetical data blow with 3 clusters (`group`). How can I find and draw the **the pooled within-cluster, $\beta_w$** regression line? THE LINK: ( https://www.researchgate.net/publication/6274186_Centering_Predictor_Variables_in_Cross-Sectional_Multilevel_Models_A_New_Look_at_An_Old_Issue ) ## R code: --------------------------------------------------- set.seed(2) pop_mean <- 80 n_groups <- 3 groups <- gl(n_groups, 5) x <-rnorm(length(groups), 55, 15) Z <-model.matrix(~groups-1) group_means <-rnorm(n_groups, 0, 2.5) y <- pop_mean + -.3*x + Z%*%group_means + rnorm(length(groups), 0, 2) data <- data.frame(y, groups, x)