Jon Schwabish just posted a nice solution to the problem of the side-by-side bar chart. I won’t go into why they’re A Bad Thing – he does that just fine.
I wanted to put this post together because it’s something I’ve been thinking about too. My solution is slightly different. Consider the side-by-side bar chart at the top showing sales of Product A and B over ten years. Too much ink! It’s confusing and impossible to interpret. It’s really hard to see anything.
How else can we show this info and ask “in which years did B outsell A?” Simple. Do something heretical and connect the dots using a line (what? Use a line to connect discrete values? But you can’t do that!):
Because we’re so well evolved to see slopes, we quickly and easily see the three years in which B outsold A:
In this example, because it’s sales over time, I kept the years as separate panes.
With slightly different data, you can acheive the same results using a categorical slope chart. I’m doing this as part of my analytics based around the UK General Election (http://impartialityuk.tumblr.com/).