Missing Bar Charts Select points on the volcano plot and click this down to display bar chart for each point showing the proportions of missing and nonmissing records for the site as compared with the average of all of the other sites. In the example shown above, points are selected and the Missing Bar Charts () down option is used to generate the bar charts shown below. In this chart, the percentages of missing (1) and nonmissing (2) records for the site relative to the average across all sites is shown.