visualising session data

Question

I'm recording Users session data for my sites. I record login and logout dates/times along with pages viewed and country codes of where they visited from.

I'm having trouble working out which graphs should be used to display this information. At first glace it feels like it would make sense to display country codes (country code and count of sessions under that country code) as a pie chart, but when there is maybe only 1 country code in play, or one that dominates the statistics it seems that the pie chart is a bit of a pointless prensentation.

The real issue I have though is displaying the session information (times logged in, logged out and length of time viewed). At first I was thinking an area graph would be useful, but that doesn't easily deal with times when a session is just 25/10/2012 11:10:09 (datetime) rather than a length of time (2 records+) like 25/10/2012 11:10:09 & 25/10/2012 11:20:31 giving me a length of 10 minutes and 22 seconds. Am I using an area graph incorrectly or should I be looking at something more like a Bar Chart rather than any form of line graph.

Answer 1

Making graphs for data like that is not easy because there's no meaning intrinsically attached to it, so the value has to be assigned by you and then decide which format is the best yo use.

For instance, if you need periods of use, and sometimes you only have the first or second value, discard those, record how many there are so you can add that information to the legend of the graph, the inform or any other place you need it, then choose a graph that helps to visualize periods.

if you need more attention to starting times, then focus on the login period. and use something like bars. The same if you only need ending periods. You can obviously combine both in the same graph, but it may be confusing depending on the user patters, so I'd say use two differentiate and present them one on top and the other one below, aligned in a way that is easy to see the actions or the same moment.

For the situation that you mention about country codes and one overwhelming the rest, I'd go for splitting it in two different parts of the same idea/graph, for instance, you can use the pie for all of them, except the main one, and add in the legend the ratio between the first result and the second. You can use a pie where most of it is the dominant one and an arrow (or any thing you like) that points to the second one where only the non dominants are.

The last idea also works with any other graph, like bars, you may show first one with all the data, and then another one with only the similar one.

If something is just too different from the rest, it damages the perspective and makes almost impossible to really appreciate the ratios, so the best option is to single it out.