Not Gauges Again!

At least monthly I receive a request to design a speedometer graph, or to resurrect an old tutorial which once (dis)graced my web site. It’s as though I would change my mind about these gauges if someone asked nicely. Last week I received another nice request, and this post paraphrases my response.

Yes, I did once have a tutorial that showed how to make a speedometer chart. But there were a couple of reasons that prompted me to take it down. First, it was very complicated, requiring a good working knowledge of algebra and trigonometry, and I got lots of emails asking me to clarify the protocol. Second and more important, these charts are particularly ineffective in the display of information. I removed that tutorial from my web site, and it has also disappeared from the computers in my office. No use asking: it’s gone and I will not reconstruct it.

I know you were probably instructed by a supervisor to use pretty dials, and probably 3D charts as well, and pretty colors, and flashing lights, and maybe a buzzer or two. What the boss wants, in this case, is not what the boss should get.

Dials and Gauges

Here are a few articles written about how poor dials are for displaying data, and how the cockpit of a fighter jet or the dashboard of a Formula One racing car makes a poor metaphor for a business dashboard:

Down With Gauges! – Charley Kyd

The Ultimate Business Driving Machine – Zach Gemagnini

Speedometer Chart – this web site

Bullet Graphs

If you do want to use some kind of single-value indicator, you could use a bullet graph. Though it only shows one value against a background scale, a bullet graph takes up minimal space, so its use leads to greater data density. Bullet graphs are well suited for use in tables, because they can be as small as a cell in a row of data. Here are some sources about bullet graphs:

Bullet Graph Design Specification – Stephen Few

How to Make Vertical Bullet Graphs in Excel – this blog

Better Alternatives

Line charts are a better choice than dials and bullets if you should be showing data over time, instead of a single value.

A column or bar chart with appropriate background shading can take the place of multiple bullet charts (see Horizontally Banded Chart Background and Horizontal Bands in the Background of an Excel 2007 Chart).

1. Michel says:

I was one of the many that requested this kind of display, and yes it was a supervisor of mine who asked if I could create a speedometer type display.
In my line of business, aviation, these kind of displays are commonly used to indicate just one variable in order to be able to see in one quick look if the indication is within certain limits (see e.g the following picture of a cockpit display system http://www.projectmagenta.com/products/groupAB.jpg) A pilot needs to see in one glance if for the engines are working properly and an immediate comparison can be made between multiple engines.

I can construct a good working speedometer using this site: http://windowsdevcenter.com/pub/a/windows/excerpt/excelhacks_chap05/index.html

However I am not yet able to create the dial to be a single line as well as the tick marks at the values as displayed above.

Thank you

2. Michel -

For a pilot, often a single value, one data point in time, is useful. By sticking to this metaphor in a business display, you are handicapping the viewer by not providing an appropriate amount of information. It’s important to know that a value is currently in range, but it is also important to know how well it stays within range, and whether it’s rising or falling. Ironic that an appropriate graphic takes so much less effort than a complex ineffective one.

3. Alessandro says:

Jon, as soon I saw this topic I remembered I made some charts for my work using your speedmeters one a few years ago. All I know about charts I have learned with you since your first site and no doubt you are a great professional, so this my chance to say “thank you so much!”… In the first time I saw this kind of chart I liked it so much for the visual impact… but I need to agree with you about havind others more efficient ways to demonstrate something. Anyway I have your tutorial (in excel) how to make it with a little modification, I think. So, if you allow me to send it for Michel, I will do it with pleasure.

4. Alessandro -

I appreciate your offer, but I feel it is midguided to spread this ineffective technique. Please honor my copyrights and refrain from sharing my tutorial with anyone.

Thanks. And thanks for reading my site for so long.

5. Michel says:

@Alessandro
Thanks for the offer,
nice visualization btw, office 2007+?
I still use 2003

Searching further on the web I found some scattered information and guides making similar graphs, by combining them and using coomon sence I can now fully reproduce the above graph. I agree with Jon on the misleading representation and ineffectiveness, but as stated in my line of business it is widely used to get a immediate “feeling” of a situation” for one single parameter.

6. Michel -

That must be a warm and fuzzy feeling, because it’s not based on true understanding.

7. Michel says:

No fuzzy feeling, honestly

It is used in the aircraft cockpit, just think of it like this.
would you prefer a bar chart in your car to indicate the speed with which you are driving?

8. Michel -

Here’s where the metaphor fails. We are not piloting an aircraft, nor driving our car. We are managing some aspect of our business.

Suppose I have the nicest gauge chart imaginable. It shows red-amber-green ranges, and one or more needles indicating the current situation.

We’re monitoring production on an assembly line. Below 15 units is red, above 20 is green. Our needle is at 18. What does it mean? It means we are in the middle zone. What else does it mean? Nothing. Is it enough information? maybe, but probably not.

Now imagine a boring old line chart. It may have colored bands in the background, or horizontal lines, indicating the levels of 15 and 20. The most recent value of 18 does not stand alone. We can see backwards in time, to see whether that 18 is representative of our extended history, whether it is an outlying value, or whether it is the latest in a trend of steadily decreasing (bad) or increasing (good) behavior.

Why does the pilot survive with just gauges? Due to extensive training and experience, our pilot is mentally immersed in the operation of that aircraft. He can can deal with single value gauges, showing only the current moment in time, because he has intimate knowledge of the trajectory of all of these readings, and he knows he’s been increasing altitude or adjusting airspeed. He can compare his knowledge of the current flight and the instantaneous values on his gauges to his mental image of how a flight should proceed.

Driving our car, we feel how the ride is going, we can feel whether we are accelerating or decelerating, we know we’ve been adjusting our speed, and the gauges confirm the state of our adjustments.

With a typical gauge, all we have is our value of 18, and we know almost nothing. Do we reprimand the operator who only makes 18 parts this shift because he left early due to illness, when all his other history shows values of 25? Do we punish an operator who only makes 18 parts, when a week ago he was only making 12, but due to training has been improving by 2 parts each shift?

Your boss may see the pretty dial, and think, “My subordinate has made me a pretty chart. I like the chart, so I feel undeservedly good about my understanding of my business.” But does he understand the context of the value of 18? No, and he shouldn’t be forced to remember last week’s values: they should be present in the dashboard.

So one day, make your regular cockpit video game, then show the equivalent but improved dashboard which includes the historical and situational contexts. Replace those pretty gauges with useful line charts. Say to your boss, “I thought this might be an improvement, because you can see how this value compares to yesterday, last week, last month.”

Bit of a rant, but I hope you see my point.

9. Nihao says:

Hi Jon,

I do not understanding your point,but I think the speedometer graph is very nice to display the data, I would like to create this chart,however, it is so hard……

hi Alessandro,

Would you share me the tutorial? I do think this is some useful for me.

10. Nihao -

The point is that while these gauges may look nice, and they may even remind you of driving a car, they are very poor at conveying information.

Alessandro will honor my copyrights and not share the tutorial.

11. Alessandro says:

Yes Jon I will honor your copyrights… I have learned so much here with you that I couldnt never to do something against what you have asked me. Dont worry about that please.

12. DQKennard says:

I felt a bit sorry for Jon, reading the comments on this thread. Jon says “gauges are bad; there are always better choices.” Responders say, “But how do I make them?” Jon says, “Gauges are bad for such and such and such reasons.” Responders say “But they’re nice. How do I make them?”

Maybe, since they’re supposed to use a driving metaphor to convey a snapshot of “right now”, but don’t get the extra information a driver has to give them context, they need extra stuff added. Like, if it’s in the “Red zone” there’s a rrrevvvvving noise. Or, if there are outside influences causing instability, it could trigger a rumble in your force feedback mouse, or your chair. If we had Smell-o-visionTM, there could be a burning rubber or hot metal smell as appropriate.

13. Great idea. How about the next person that asks for gauge instructions gets 10,000 volts through his keyboard!

14. wynand says:

Jon maybe people are confusing the use of guages

The only use I can see for gauges are to show colors e.g the risk is high (red), medium (yellow), low (green).

For data and metrics is serves no purpose

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