thanks kimmo I managed to get the desired result by first plotting the medians and then adding the means through the user defind function posted in thread you mentioned (here it is http://r.789695.n4.nabble.com/Adding-mean-line-to-a-lattice-density-plot-td4455770.html#a4456502)
# start dotplot(variety ~ yield | site, data = barley, scales=list(x=list(log=TRUE)), layout = c(1,6), panel = function(x,y,...) { panel.dotplot(x,y,...) median.values <- median(x) panel.abline(v=median.values, col.line="red") }) addLine<- function(a=NULL, b=NULL, v = NULL, h = NULL, ..., once=F) { tcL <- trellis.currentLayout() k<-0 for(i in 1:nrow(tcL)) for(j in 1:ncol(tcL)) if (tcL[i,j] > 0) { k<-k+1 trellis.focus("panel", j, i, highlight = FALSE) if (once) panel.abline(a=a[k], b=b[k], v=v[k], h=h[k], ...) else panel.abline(a=a, b=b, v=v, h=h, ...) trellis.unfocus() } } mean.values<-tapply(barley$yield, barley$site, mean) addLine(v=log10(mean.values), once=TRUE, col="blue", lty="dotted") # end but back to my previous question I still not understand why the plot of medians is working fine BUT NOT of the means (apparently messing up panel positions and also values): no clue for this! I've been trying also with the use of layout() in latticeExtra but without results... anyone can clarify me these (strange for me) issues? max -- View this message in context: http://r.789695.n4.nabble.com/how-to-add-a-vertical-line-for-each-panel-in-a-lattice-dotplot-with-log-scale-tp4632513p4632692.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.