Mar 182014

Note: Since writing this post in 2014, I have, in fact, become a fan of sparklines. That said, I continue to see many instances where I think the dashboard author could present data more clearly using a different approach. Make sure to read the comments at the end of the post.

I’ve never been a big fan of sparklines and I’m a bit concerned with how often they are cropping up in dashboards.  While I appreciate that this chart type provides a compact mechanism for showing how a collection of measures wax and wane over time, I believe there are many cases where other chart types will do a better job getting the message across.

Stephen Few’s Dashboard Design Competition

I’ve been reading the second edition of Stephen Few’s Information Dashboard Design and was drawn to a discussion of the design competition Few ran in 2012.

Consider this data snippet from the competition where we see student test performance over time:

Student test results

Student test results

The winning entry, the runner up, and Few’s own solution rely heavily on sparklines to present this and similar data.

My Attempt at Sparklines

I’ll be honest that I have a very difficult time being able to understand any of the sparkline renderings from any of the design entries. Perhaps if I took a stab at myself…?

Consider my attempt below:

Student test results rendered using sparklines

Student test results rendered using sparklines

I ask you if you can see — at a glance — that the best performing students are at the top and the lowest performing students are at the bottom?  Can you see that Regan Petrero (about 60% of the way down the list) received “C”s for his first three assignments, a “B” for the fourth assignment, and a “D” for the fifth assignment?

Granted, I can try to make certain things stand out better by adding banding and not having the axis start at zero, but even with these additions I’m not able to come up with anything that tells as clear a story as what I get with a simple highlight table.

Student Data, Take Two – A Highlight Table

Here’s the same data rendered using a highlight table:

Student test results rendered using a highlight table

Student test results rendered using a highlight table

I can see immediately that Holly Norton is a straight “A” student, that Donald Chase just missed being a straight “A” student, and that Xu Mei has had some wide fluctuations.  The chart is compact, easy-to-read, and I can discern both comparative performance and relative performance with very little effort.

What about Frederick Chandler?

If you look at my sparklines tendering  you will see that there may be an interesting story with respect to Frederick Chandler and the third assignment.  In the sparkline you can see there was a big dip; in the highlight table you can only see that Mr. Chandler received an “F”.

It turns out that Mr. Chandler received a zero on the assignment.  Is it important to show this, versus just showing a failing grade?  I don’t know the answer, but if it is important then we can create a six point color scale, as shown here:

Mr. Chandler’s zero, for all the world to see

Mr. Chandler’s zero, for all the world to see


See For Yourself

I present the sparklines and highlight table side-by-side in the dashboard below. Have a look and let me know what you think.  If you have a way to make the sparklines “sing” better by all means please share it.

Please realize that I’m not suggesting that you should never use sparklines; I only ask that you consider whether sparklines are the best way to show what is important about the data before you publish. I very much encourage your to explore other options.


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  6 Responses to “Sparklines, Schmarklines”

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  1. Interesting discussion, but I think you’re drawing an overly general conclusion here. First of all, what you have here are not really sparklines (which are supposed to be used in text), but small multiples. And just because they’re small doesn’t mean that the aspect ratio doesn’t matter, or that lines are the only way to show the data. You still need to look at what works.

    Using bars instead of the lines would be much clearer, and would give you a sense of the absolute values that the lines don’t give you. You could also color those bars, just like your heatmap, so that you’d see the grades.

    I’m not arguing that the heatmap doesn’t work, because it clearly does. But the comparison with the small line charts is not entirely fair.

    • Robert — I’m not suggesting one should always use a highlight table, or that sparklines are never the best choice, but if you look at Few’s solution (and the one’s he anointed as worthy”) they all use sparklines and I think they are very difficult to read. As for using bars in this case, please show me, with this example, how they would work better. I would love to see a good alternative.

  2. I think you’re right to call out situations where people use sparklines assuming they are the best approach. My first reaction to this post was “Well, you only have 5 data points in the time series, of course they won’t work.” Sparklines, for me, work better when the time series is longer. 

    But then I went to Stephen’s blog and looked at his solution. And, oh yes, it too uses sparklines for a five-point time series. I’m inclined to support you in this case that a heat map might have been easier to read. 

    In Stephen’s defence, he’s written on ways to improve sparklines (I refer to his article on bandlines from last year:

    • Andy, I’ve read the article, and it’s cited heavily in Few’s dashboard design book. Few uses bandlines and the ever-so-nifty sparkstrips to convey the distributions in his own solution. But even with these additions I believe his solution is one tough read. Joe Mako politely called me out for creating a bit of a strawman with the sparkline example I constructed. Yes, I could have put another hour or two into the view and added the bandlines and other visual aids but it would have been wasted effort. Now, if the data contained five years of widget sales broken down by month or week then I would probably reach for the sparkline.

  3. Great post. I am now quite interested in learning how I can work “Schmarklines” into my every day conversations…

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