If several box plots are to be displayed on a graphic where the X-axis represents a unique level, but one which is continuous (like per-year over a very long study) is there a well known way to condense a large number of boxplots aside from the obvious of aggregating up by large subsets of the X?
Illustrating @gung's suggestion, here are boxplots (made in R)--one for each of 10 'years'.
Each boxplot shows 12 (simulated) 'monthly' values of a variable
x, which is gamma
distributed. Gamma shapes increase gradually from 2 to 8 during
the 120 months, and rates from about .32 to about .45.
Red line segments connect the averages for the 10 years. Such a graph is still clearly readable with 30 years instead of 10 (second figure).
# R code for first figure set.seed(329) # for reproducibility Month = 1:120 shape = seq(2, 8, len=120); rate = seq(.1,.2,len=120)^.5 x = rgamma(120, shape, rate) Year = rep(1:10, each=12) MAT = matrix(x, byrow=T, nrow=10) # a row for each year a = rowMeans(MAT) # 10 averages boxplot(x ~ Year, col="skyblue2", pch=19) lines(1:10, a, type="l", lwd=2, col="red")