library(ggplot2) data(AirPassengers) d <- data.frame(Year = c(floor(time(AirPassengers) + .01)), Month = c(cycle(AirPassengers)), Value = c(AirPassengers)) d$Month <- factor(d$Month) levels(d$Month) <- month.abb tmp <- d names(tmp)[2] <- "MMonth" p <- ggplot(data = d) + facet_wrap(~ Month, nrow = 3) + geom_line(data = tmp, aes(x = Year, y = Value, group = MMonth), color = grey(.7)) + geom_line(aes(x = Year, y = Value), size = 1.5) p + theme_minimal()