Go Figure: Visualizing Big Data
Inside baseball perhaps, but in my other blog, I go into some detail about a figure I made for one of my papers. In the figure, I’m trying represent data from a few hundred hours of heart rate monitoring. I realize its nothing like the Big Data of web analytics, but it’s reasonably large by the standards of the field. If you have any interest in how the science sausage gets made, have a look.

Interesting visualization. Do the width of the horizontal scans correspond to the daily cycle or are the abritrary?
The details are explained here. I should have made that more clear by linking directly to the appropriate post on my other blog. To answer your question in brief, the x-axis is time.