Stephen Few has long proposed his bullet chart as a replacement for gauge-type reports. Steve argues that bullet charts are more efficient (take up less space) and encode more and more accurate information than a gauge or speedometer type chart. I’m still unconvinced, especially since I’m not a fan of a visualization that requires retraining of the end consumer. I’d much rather use something that the end consumer ‘gets’ right away.
That being said, I haven’t written a visualization post in a while and just because I’m not convinced on bullet charts doesn’t mean that you aren’t and that you might not be looking for a way to create them in Excel. My version is a combo-chart using both a scatter plot and stacked horizontal bars so the order in which we add data and chart elements is important.
BTW, I am going to assume that you have a passing familiarity with Excel and its charting utilities so don’t be surprised when I outline the steps to take (insert a scatter plot) rather than give detailed instructions (select data in cells A1:B2, go to ‘Insert’, click on the Scatter Plot drop down and select the scatter line with no point markers).
Step 1: In this first step, we will add the data for the scatter plot and create the default scatter plot graph. In this example, we are using the scatter plot to set a goal line for the overall bullet chart.
So, when we create the initial scatter plot, you’ll see that the x-coordinates are ‘80′ - this is my target. In this case, I happen to be charting the performance of the Homepage Retention Rate (1-Abandonment Rate) and I am shooting for 80%. I happen to be using whole numbers for simplicity’s sake but it could just as easily be percentages. Don’t worry about the vertical alignment of the line just yet, we can adjust it - if needed - later when we are closer to the completed graph. Notice that I haven’t removed any of the chart junk yet either, that will happen in a later step.
Step 2: Now we need to add the data for the horizontal stacks and the stacks themselves. We will have 3 bars (Top, Middle, Bottom) with 4 sections each.
When working with combination charts, adding the new data points and chart types can be tricky. In the screen shot to the left, we’re looking at the completed process, I’ve excluded the intermediary step of what the data looks like when we first add it.
In order to add the stack data to chart we first select the data from all four of the stack columns and copy it. Then we select the chart and use ‘Paste Special’ to paste the data as ‘New Series’ with ‘Values ‘Y’ in columns’. This will paste our stack data in as new scatters. We then select each of the stack series and change it’s chart type to ’stacked bar’.
Ok, now that we’ve talked about how to add the stacked data to the chart, let’s talk about the data itself. In the top row, the first data point is ‘50′ - this is our floor (minimum acceptable value). The second data point for the top row is always zero. We need this second stack element for visual handling on the center stack (see the little green block in the center bar) when it is less than our minimum. Oh, I’m also not going into excruciating detail on the formulae used in the data set, they are fairly straight forward and you can take a look at them when you download the spreadsheet at the end of this post.
Step 3: This is easy, set the gap width on the bars to ‘0′ so that they are slammed up against each other.
Step 4: Time to take out the chart junk.
Remove the vertical axes, and the secondary horizontal axis.
Remove the horizontal lines.
Remove the legend.
Remove the plot edge lines
Set the scaling on the primary horizontal axis, set the axis-line to none as well as the major tick marks to none.
Step 5: Apply consistent and valuable color-coding to chart elements.
The blue stack becomes our representation of ‘Actual’ (e.g. the bullet). The background elements are encoded in shades of gray.
Up to 50% is nearly black - remember, this is our floor
From 50% to 75% is about 50% gray - this is our marginal performance section
And finally, from 75% to 100% is light gray (20%) for acceptable performance. I’ve also changed the target line to full black, it stands out nicely against both the light gray and the blue.
Step 6: Resize the chart.
So far, our chart hasn’t look much like a bullet chart has it? Well, that’s pretty simple to take care of. In this example, I’ve held the horizontal length the same but compressed the vertical height. Now we have something that very definitely is looking like a bullet chart.
Step 7: Add a text label and center align the chart to the text label.
Ok, so what I’m really doing is adding a text description, and the actual value of my metric in the two cells to the left of my bullet chart. Then, I’m massaging the bullet chart into alignment (hopefully) with the text. Notice that the value I’ve put in the label (86) doesn’t match the value in the chart, we’ll fix that in the next step. You might have also noticed that in this step, I removed the final piece of chart junk from my chart - the chart area border. Up until now, it was helpful to have the border for moving the chart around, but now that I have it correctly situated, I no longer need it.
Step 8: Synchronize label value to chart value.
Yep, you guessed, that’s a fancy way of saying set the first value of the center stack equal to the text label value (=D89). Now, I can enter a new value on the label, and the chart will update automatically.
Step 9: Obscure the chart data.
We had to jump through a lot of hoops to get to this graphic, but we probably don’t want the report consumer to be thinking about those hoops, so set the text color of your chart configuration data to ‘white’, effectively hiding it from the consumer.
Step 10: Rinse & Repeat
Ok, so there’s my step-by-step on how to create Bullet charts.
What? You want the spreadsheet? Well, since you asked so nicely…
Download the Excel 2007 version or Download the Excel 2003 version
