I have an archive of 20 years of email data that I am analyzing. Currently, I have grouped each email by day and hour, because I want to be able visualize how much email is sent at given hours of the day. Specifically, I am trying to answer the question, "Are some hours of the day more likely to have email than others?" My first approach was to create a line plot of the mean.
Although this gives a good characterization of the "average" behavior (and reflects my expected trends), it does not give any characterization of the variation within an hour. Just from looking at the data, I know that most days have no emails sent at all, so most of the time the data is zero (in fact, plotting the median results in a horizontal line at 0 posts). The distribution for each hour is definitely not normal; there is extreme skewing towards zero for every hour.
My next thought was a scatter plot with high transparency, plotting each day's # of emails for each hour. Although better, I still think this struggles to convey the story of the data meaningfully:
Does anyone have better ideas on how to accurately capture the data in a visualization? To me, it seems like there are clear variations during the day, but most days have zero posts.