Sunday, April 2, 2017

Backwards Bar Charts

Recently, someone shared a visualization from Periscopic about the Trump Emoto-coaster. While the subject matter itself was not of particular interest to me, I did like the presentation of it.

Strap yourselves in. Your hands must be this small to ride this ride.
The line chart at the top made me think about the rises and falls within a school year. March seems like an especially cruel month, with teachers' tempers growing short. (Just ask me about how I ended up in a conversation with a five-year old about why we need to wear pants at school.) How do attendance and discipline intertwine? And, when I looked at the horizontal bar cum sparkline plots shown above, it also made me wonder what we would see if we plotted individual classrooms over time. Maybe something like this:

Let's say there are four teachers at a particular grade level in a school. If we looked at the number of student absences and office referrals from the beginning of the year to the end of the year...what might we see?

If I was a principal, I might use something like this to either look for "hot spots" in my school that I might not know about...or monitor how well my school improvement initiatives are being implemented at the classroom level...or even to show staff for input. If I was a teacher, this might give me a general way to compare outcomes in my classroom. It might also piss me off (This just shows you that I have ALL of the bad kids!).

My challenge was how to build this. At its most basic level, this is a floating bar chart. And Ann Emery has a great tutorial for doing just that in Excel. But I didn't take that particular route this time because of how I need these charts to lay out. You see, absences for any given classroom total no more than 70 in a month...but referrals are no more than 13. Excel isn't going to let me push the edge of the chart off the lefthand side of the worksheet if I keep the x-axis the same on both sides, meaning I ended up with a ton of blank space. I suppose I could put attendance on the left and discipline on the right, but hey, what's Excel without some challenges?

So, how do you build a backwards bar chart?

Create your horizontal bar chart the usual way, then fuss a little bit with the axis settings.
Once you do this, then remove the gridlines and axes themselves, you'll be able to position this bar smackdab against the other one. You know it's worth can work it. Just put that chart down, flip it, and reverse it.

Another to know about this chart is the addition of the line down the middle. Since I deleted the gridlines and axes, I need some sort of visual between the bars. So, a simple line shape in grey 1.5 pt is all that was added.

In terms of labels, I'm going to leave them off. If you understand how one is laid out, then you can understand a whole school's worth. The numbers themselves aren't the big idea with this visual. It's the patterns and comparisons we're after. When we've identified those, we're ready to ask some deeper questions and dig into the numbers in a different way. These charts are the starting point for conversations...not the end...even if that seems a little backwards.

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