Increase in tag density per PubMed citation with increase in number of CiteULike posts per citation. Each vertical box and whisker plot describes the distribution of the number of distinct CiteULike tags associated with PubMed citations tagged by the number of people indicated on the X axis. For example, the first plot, at X = 1, describes the density of tags per citation assigned by just one person while the second plot, at X = 2, describes the density of distinct tags per citation assigned by the aggregated tags of 2 people and so forth. The median of the distribution is indicated by the horizontal line, the upper and lower boundaries of the box indicate the medians of the first and third quartiles (such that 50% of the data lies within those boundaries), the whiskers extend either to the extremes of the observations or a maximum of 1.5 times the interquartile range, and circles indicate outliers.
Good et al. BMC Bioinformatics 2009 10:313 doi:10.1186/1471-2105-10-313