Bar chart or Line? Scatter plot or box plot? These are the questions we ask ourselves when we set out to make a chart. In this article let me tell you how to pick a chart type so you can make best charts for every situation.
Why is it important to pick right chart?
Because right charts lead to right decisions. We use charts to tell stories, evaluate alternatives, understand trends or find-out if everything is normal. So, an incorrect charting choice can lead to poor judgment of the messages where as a correct chart can lead to right and faster decisions.
How to pick a chart type:
Chart making process can be divided in to 4 steps
- Find-out what you want to say?
- (Re)arrange the data
- Prepare the chart
- Format the chart
1. What is the purpose of this chart?
This is the first and most important step in chart preparation. You must ask yourself, “what is the purpose of this chart?”. Once we know the clear reason why the chart should exist, we will naturally be able to select the correct chart type for that reason.
But I realize that finding the reason itself can be a bit tedious. So I have listed down 6 common reasons that we often have to make a chart:
- to Compare
- to show the Distribution
- to explain Parts of the Whole
- to tell the Trend over time
- to findout the Deviations
- to understand the Relationship
Let us understand these reasons along with the type of charts that go well with these.
1. To Compare:
What it means? You want to compare one set of value(s) with another.
Examples:
- Performance of Product A vs. Product B in 5 regions
- Interview performance of various candidates
Charts that can be used for this reason:
- Bar Charts,
- Column Charts
- Scatter Plots
- Pie Charts
- Line Charts
- Data Tables
2. To Show the Distribution
What it means? You want to show the distribution of a set of values (to understand the outliers, normal ranges etc.)
Examples:
- Distribution of Call waiting times in a call center
- Distribution of bugs found in 10 week software testing phase
Charts that can be used to show distribution:
- Column Charts
- Scatter Plots
- Line charts
- Box Plots
3. Parts of Whole
What it means? You want to show how various parts comprise the whole
Examples:
- Individual product sales as a percentage of whole revenue
- Browser types of customers visiting our website
Charts that can be used to show Parts of Whole:
- Column Charts
- Bar Charts
- Pie Charts
- Data Table
4. Trend over time
What it means? You want to understand the trend over time of some variable(s).
Examples:
- Customer footfalls on the last 365 days
- Share price of MSFT in the last 100 trading sessions
Charts that can be used to show Trend Over Time:
- Column Charts
- Line Charts
- Data Table
5. Deviations
What it means? You want to see which values deviate from the norm.
Examples:
- Failures (or bugs) in the context of Quality Control
- Sales in Various Stores
Charts that can be used to show Deviations:
- Column Charts
- Bar Charts
- Line Charts
- Data Table
6. Relationship
What it means? You want to establish (or show) relationship between 2 (or more) variables
Examples:
- Relationship between Search Phrases and Product Purchases in your website
- Relationship between in-store sales and holidays
Charts that can be used to show Relationship:
- Scatter Plot
- Line Chart
- Data Table
How to pick a chart type when you have more than one reason for the chart?
Simple, use common sense. If I were you, I would either cut down the messages to one or make 2 charts (each conveying one message). If that is not possible, I would consider using dynamic charts or combination charts.
2. (Re)arranging the Data
Even when we know the message and corresponding chart, sometimes, our data may not support us. We then have to rearrange the data. Using excel formulas, pivot tables, tables and data cleaning tools we can easily massage the data.
Once we have the data in required format, we proceed to step 3.
3. Prepare the chart
Since you have already picked the chart type in Step 1, this is very straight forward. Most of the regular charts are available in MS Excel as default charts. You can insert them with few clicks.
But for some special chart types, you may have to prepare the chart by helper series, formatting etc.
4. Format the chart
While most formatting is done as per individual taste, there are some ground rules that apply on almost all charts. Here they are,
- No non-zero axis scale on bar charts [reasons and discussions]
- Make subtle grid-lines (or remove them) [how to remove grid lines]
- Add labels to important points [labeling techniques]
- Add descriptive, bold titles
- Position axis, scales at the right places (for eg. y-axis to the right on a large time series chart)
- Use simple, easy colors
A final word:
The ideas in this post are meant to be guide lines, not final words in the world of visualization. While these rules can help you make a good chart, a great chart take so much more. Knowledge of your data, Passion for what you do and Genuine focus on your audience’ needs can make your chart truly outstanding. All the best.
References:
Communicating Numbers – White Paper by Stephen Few [PDF]
Resources & Further Help:
- Chart chooser – Juice Analytics
- Data vis 101 – How to choose a chart – Hubspot
- Selecting right char type – KD Nuggets
- Charting Principles
- Charting Tutorials from Peltier Tech
- More articles from Stephen Few
- Charting Wisdom from Jorge Camoes
What is the process you use for Chart Selection?
I would love to know the process you use when selecting a chart type. Please share using comments.
37 Responses to “Pie of a Pie of a Pie chart [Good or Bad?]”
If I could have the same quality of graphics and illustration in Office Apps, I would certainly use it.
If I could have the same quality of graphics in Office Apps (Excel, PPT) I would certainly use it.
Chandoo,
First, let me say I love your blog. I like this post, and I think that technically (in terms of readability of data) your argument is correct. The bar of bars, and the table, are much better for readability and accuracy, and as you say would be much easier to produce.
But these points ignore the context of the chart. If the chart was part of a scientific paper, your solution would be a valid one. The context in this case is an illustrated atlas of wildlife. A companion graphic to go with written text. The importance of aesthetic goes up over readability and accuracy. Much of the data and points (I assume) will be covered in the text.
There's always a pure technical tufte-esque argument. But I sometimes think it ignores the value of aesthetics. (Which I admit are quite subjective)
Great post though. Thanks.
The Treemap makes the scope of the data much clearer! The 3D pie chart depiction is deceptive.
This reminds me of the videos ive seen on the internet where it compares the relative sizes of the earth with the larger planets, then the sun, then other stars in the galaxy. Eventually there is an image showing the largest star in the sky with a little pixel representing the sun.
My point is if you varied the size of the charts it would help convey the message. The first chart (salt vs fresh) would be the biggest and the rest would be arranged in descending order. I feel this would be more accurate.
It may be helpful to consider the advice of Steven Few and Edward Tufte regarding pie charts in general. To summarize, they are seldom the most useful way to present data. Here's Few's thoughtful piece on the subject.
http://www.perceptualedge.com/articles/08-21-07.pdf
Try putting the percentages on the bar charts instead of actual amounts. Lakewater would be .013 % instead of 52.
That is very good pie chart example.
Please send example file if it is possible.
It will work , even though colors may be confusing , it can be labeled well . Also it can be called as the drilled chart , as it drills in information further , like the first chart may show business in a region , second may drill into a particular region , thrid may further drill into wat products are there in that region . It works well for me , i would more vote for the 2 nd option .
Overall all this site is awesome ,
p.s : just like me
The risk with pie of a pie of a pie chart is that Jon may have a seizure by looking at it. Also, it isn't easy to read. 😉
I dunno. The only thing worse than a pie chart is a cascading series of pie charts. I don't even think they really lend themselves to this sort of thing. It just becomes a big hide-the-ball game with your viewer.
Those goofy connectors between the pies are pure chart junk. I can't really tell if the second chart has 2 series or 3 - because the connector is a different color than the 2 labeled slices. Despite that, even whereas the drill down kind of works, still the individual components suffer from the same old weaknesses that 3d pie charts have.
Use a large bar chart as your "cover story", and fill in the sub points with smaller bar charts - or even go grab the Fabrice SFE project for extra butter. Use page orientation, color, and some text styles to guide your audience through the drill downs.
FWIW, if you check out the guy's site, you can find several other truly mortifying charts:
http://www.andrewdavies.com.au/index.html
The methane emissions one is particularly heinous. Although, I'm kind of debating what I think about the 'Glacier Changes" chart. I'd kind of like to see the data on that to see how it would look in a more traditional horizon chart.
Thank you, that was scary. I don't understand the "Glacier changes" Chart at all...
Its a very nice way to represent the data, especially when we have sets and sub-sets within the data.
I like these!
Except for the fact that they aren't dynamic and hence must be setup manually each time
It would also be nice if they could be interrogated as in select a different segment and the new data falls out automagically, but then none of the standard Excel charts do that either.
I'd like it better if the bars were stacked. How about this idea (I hope I can convey it in words):
First bar is vertical and stacked.
Second bar is horizontal, stacked horizontally and the same proportion had it been on the first bar.
Third bar is vertical, stacked vertically and the same proportion had it been on the second bar.
Then it would really look like you are zooming on the chart, like the Powers of Ten video, or maybe like the golden ration spiral.
These looks shunting but setting up for each step makes kicks them out. However if these can be arranged automatically by native excel or by VBA, these will be the part of my "Archery"
I agree with Chandoo's Suggestion about the Bar Graph which represents data in a very appropriate manner. Even I prefer doing the same. I seldom use Pie Chart unless required.
That's a real nice example of a missleading infographic. But to be honest, I think chandoos suggestion is not much better!
Why are pie charts bad? I think because they don't show the real size-relations. The biggest pie in that example ist 300k big. The 2nd one has only the size of 10k, about 3% of the first one. Niether the pies nor the bars show the real sizes. I jnow, it's hard to show the sizes because the values of the second and the third pie are so small. But that's what visualization are about - showing relations to allow the reader to see the real sizes!
So how to show the real figures?
First possibility is o use a 1:1 scaling. Well then, you need a very big screen to show also after a 90° rotation, wihich I would prefer because it's a structural comparison and not a timeline. Maybe that solution is not the perfect way.
The other chance you have is to zoom in but to really show that you zoom in! http://www.pro-chart.de/images/Water_Fall.png maybe gives you a first impression what i mean. (i was a quick try, done in 10 minutes)
The next way is, maybe to fold the bars like in the financial report 2011 of the Post of Switzerland page 22. That chart is based on an excel chart. Maybe can explain you how to do it 😉
Financial Statement: http://www.post.ch/en/post-startseite/post-berichterstattung/post-berichterstattung-service/post-berichterstattung-downloads/post-gb-2011-finanzbericht.pdf
page 22: http://www.pro-chart.de/images/FS_Schweizer_Post.png
A way that is not so very common is to divide the bars in a lot of single datapoints. So maybe the 390k bar then consists of about 5,000 single datapoint. That's not possible - it is! Have a look:
http://www.pro-chart.de/images/Dotted_WF.png
It's pure excel!
Now one single point ist 0,2% of the whole (in the example above). Add more datapoints and you can visulize the very big and the very small numbers!
Wish you a lot of fun - visualizing with excel can be very powerful!
Joerg
...if you would like to know how these charts work, just send an email to J.Decker@pro-chart.de
Hey Joerg,
I don't dig so much the dotted waterfall thing. But this is kind of awesome:
http://www.pro-chart.de/images/FS_Schweizer_Post.png
Can you help me on the bar of bar graph? Would it be possible to create that from pivot table? Can you show me how to create the bar of bar graph?
do nothing but say "Awesome!"
You are a Rock star.....This seemed an answer as if someone was reading my mind and just had the solution to my questions on what I exactly was looking for .....What a Fab !!
can u explian me step by step
Can anyone please explain how to make this chart please.
Do you mean the pie of a pie chart or the folded bar chart?
Joery PIE OF PIE Chart please
Can someone please explain how to make PIE OF PIE Chart.
@Mandeep
The last line of the post is:
PS: If you want to know to create this pie of pie of pie chart in excel, see here.
Due to forum migration, link is now:
http://chandoo.org/forum/threads/multiple-pie-chart.7343/
Hi... i love these charts.... can any one show me how to draw these charts in excel 2010
@Vamshi
The very last line of the post refers you to:
PS: If you want to know to create this pie of pie of pie chart in excel, see here. http://chandoo.org/forums/topic/multiple-pie-cahrt
Where is the attachment....it used to be there...i have seen this before but now i am not able to find...
See this:
http://img.chandoo.org/playground/WaterDistribution-chandoo.xlsx
And this:
http://chandoo.org/forum/threads/how-do-you-create-this-chart.9743/
Normally I don't learn post on blogs, however I would like to
say that this write-up very compelled me to try and do so!
Your writing style has been amazed me. Thank you,
quite great article.
This is very impressive, I would like to learn how to build this for myself. I have tried for some time now, is there a step by step process on how to create these waterfall pie of pie charts?
I am novice to excel and use it very seldom. But your blog contains to the point information one needs to get going.
I was searching for a trick to do a Pie chart drill down - for example the first pie chart shows how the prices are distributed between perishable and non-perishable items.
Now if we want to know how the perishable items are distributed - one can click the segment and it will draw another pie chart with distribution of all different perishable items (milk,meat,fruit,veg etc)
So do you have any such trick?
Regards,
electrojit
I like the look of your pie of pie of pie chart, although I understand that the relative size of each pie does not represent the actual percentages.