It all began with my Excel Dashboard Tutorial – Making a dashboard with player statistics. I have used bar charts with axis whose minimum is not zero, to create a dramatic effect in the charts. See below:
Jon Peltier commented saying that,
Rule #1: Bar and column chart value axes should start at zero. Since the lengths of bars and columns represent their values, starting at a position other than zero will lead to a misleading display.
As always Jon raised an excellent point. I liked it so much that I wanted to get your opinions on this axis scaling issue.
What do I think about this visualization rule ?
First the positive points about the rule:
- If you start axis at non-zero values, it gives a wrong impression about the data. In my example above you might end up thinking the top value is actually 10 times that of bottom value.
- The rule helps easy interpretation of data, since everything starts at zero.
Now the negative points about the rule:
- Not all data starts at zero (like the above with values ranging from 8000 to 12000). So when you create a bar chart for the data (why only bar charts, because they are easy to make and read) often you end up creating charts from which making out any analysis could be slightly difficult
- Breaking this rule helps in creating dramatic effect on your charts, one of the reasons we use them. Often when you use data with narrow range, creating dramatic effect could be difficult. Axis adjustments can help (you may want to try logarithmic axis scale as well)
Finally, I think this rule can be broken as long as we have right data and make alternative arrangements (like adding data labels) to ensure correct interpretation. Since this is a standard people have come to expect, it is better to make it clear to your audience about the axis range.
What do you think about the charting rule: Bar and column chart value axes should start at zero.
18 Responses to “Best Charts to Compare Actual Values with Targets – What is your take?”
Great post. I can't vote, though, because the answer I want to put down is "it depends". As with all visualisations, you've got to take into account your audience, your purpose, technical skills, where it will be viewed, etc.
I'm with Andy: It depends. Some I would use, some I might use, some I won't touch with a barge pole.
Naturally I have comments 🙂
The dial gauge, though familiar, is less easy to read than a linear type of chart (thermometer or bullet). It's really no better than the traffic lights, because all it can really tell you is which category the point falls in: red, yellow, or green.
By the same token, pie charts are so familiar, people don't know they can't read them. Remember how long it takes kids to learn to read an analog clock?
Bullet charts don't show trends.
With any of the charts that have a filled component and a marker or ine component, it makes more sense to use the filled component (area/ column) for target, and the lines or markers for actual.
[...] Best Charts to Compare Actual values with Targets (or Budgets … [...]
I voted for #6 even though I agree with the other comments that it depends.
The majority of the votes are for the #2, thermometer chart. I still have yet to understand what happens when you are above plan/goal, which was brought up in yesterday's post.
Also, I agree with Jon in that it would be better to flip the series and make the filled part the target or goal and the line or marker the actual.
I am also a fan of using text when appropriate if the data is among other metrics in a type of dashboard. Calling it out by saying actual and % achievement is a good option.
Another "it depends" vote. Are you just looking at one or are you comparing a number of targets with actuals? You didn't include a text box. The problem with sentences is that they can get lost in a page of gray text. A text box can call attention to the numbers and line them up effectively.
I'm with Jon: "Some I would use, some I might use, some I won’t touch with a barge pole" and I'm surprised that some of your readers voted for the last group.
Jon says:
With any of the charts that have a filled component and a marker or line component, it makes more sense to use the filled component (area/ column) for target, and the lines or markers for actual.
Why does this make more sense? I like 6 the way it is, although I would use a heavy dash for the plan/target marker.
"It depends" is also my take. What I usually try to drill into my clients dashboard design is the fu ndamental difference between spot results (am I on target for this month) and long term trends.. I always try to create 3 different set of graphs to represent real perormance:
- spot results vs objectives
- cumulative results vs objectives
- long-term trend (moving average) mostly) to see where we're going
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Jon says:
With any of the charts that have a filled component and a marker or line component, it makes more sense to use the filled component (area/ column) for target, and the lines or markers for actual.
Why does this make more sense? I like 6 the way it is, although I would use a heavy dash for the plan/target marker.
I totally agree, Bob. I would normally favour a line for the target and a column for the actual, you can see quite easily then which columns break through the line, then.
[...] best charts to compare actual values with targets — den Status mal anders zeigen, z. B. als Tacho [...]
Thermometer charts: "Not appropriate when actual values exceed targets" - this is easily solved by making the "mercury" portion a different color from the border, then you can clearly see where the expected range ends and the actual values keep going.
People seem to knock gauges quite a bit in dashboarding, but trying to show comparison of realtime data between operating sites and targets for each site can easily be done with a bank of gauges that have the optimal operating points at 12 o'clock.
The human eye is great at pattern stripping, and any deviation of a gauge from the expected 12 position will quickly register with an operator and attract his attention. Using a colour background, or meter edge, will also indicate the sensitivity of a particular site.
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I am wondering how will the plotting work, for some of the targets which may have been achieved before time. E.g. for the month of Jul the target was 226 and the actual was 219. So the chart will show a deficit in meeting the target by 7 points but what if this 7 may have been completed earlier in month of June. So ideally it not a deficit.