Is there an official name for this extremely simple plot, in which vertical lines indicate the distribution of some samples in a range?
The first example I have seen them referenced in are Strips displaying empirical distributions: I. textured dot strips (Tukey and Tukey, 1990) although I have never been able to actually get that technical report.
Tim is right: they are often accompanied as the rug on an additional plot to show the location of individual observations, but rug plot is a bit more general and that type of plot is not always on the rug of another plot as your question shows!
- Here is an example of using points on the rug instead of lines.
- Here is an example of the rug being points and not displaying all of the data, but only data missing in the other dimension of a scatterplot.
So a rug plot is not always a set of lines on the borders of another graph, and that type of plot in your question is not always on the margins of another plot. Here is an example of the lines superimposed on a kernel density instead of on the rug of the plot, called a beanplot. The larger lines I believe are used to visualize different quantiles (a.k.a. letter values) of the distribution.
In Wilkinson’s Grammar of Graphics it may be considered a one-dimensional scatterplot but using line segments instead of the typical default of circles. The point of this is to prevent many of the nearby points from being superimposed. If you have many points and draw them semi-transparently they eventually turn into a density strip, see the final picture in this post.
I’ve even seen them suggested to use as sparklines (Greenhill et al., 2011) in that example to visualize binary data. Greenhill calls them in that example separation plots, and here is an example taken from the referenced paper (p.995):
So in that example there are values along the entire axis, and color is used to visualize a binary variable. The black line in that plot is the cumulative proportion of red observations.