Part to a whole- Suggested Alternatives
I am visualizing data for quite a while now, and in most cases, I
find part to a whole visualizations to be the most challenging ones.
In this blog I will share my suggested alternatives + how to do it in my favorite data visualization tool- Tableau.
About Part to a whole
One of our main (some would say the only) goals as data visualizers is to deliver Maximum insight with minimum time and effort to our users.
Part to a Whole visualization aim to show part (or parts) of a variable in relation to its total. It is often used to show how something is divided up, and should always sum to 100%.
Basically, we want to accomplish two things:
1) to compare the size of the different parts and allow the user to see which part is bigger (and by how much)
2) to show the relative contribution of each part to the total
1. Pie Chart Alternative
I bet I am not the first one to tell you pie charts should be treated with caution.
When we show pie with more than 2 categories we are not providing our users a visualization that will provide them maximum insight with minimum time and effort.
Why? because our brain needs to work harder to assess the size difference between the parts, and to understand the relative contribution to the total.
looking at the relevant pre-attentive attributes (types of visuals such as size, shape, or color that our mind processes out of consciousness in milliseconds) we can tell easily which part is bigger than the others.
But, and this is important, try to assess by how much bigger? in this case length will be much easier to assess, because length is quantitatively perceived and circles are not.
Read more about it in this great article by Stephen Few.
That’s the reason why bar charts are broadly used to compare sizes, and to make things even easier we will sort it from largest to smallest when possible.
But regular bar chart answers only the first aspect (out of 2) of part to a whole right?
We still need to answer the second one which is what is the relative contribution of each part to the total!
In order to answer both, I suggest the following chart:
This is my go-to chart when I want to show part to a whole.
It allows to compare the size of the different parts and understand which part is bigger and by how much,
And it shows the relative contribution of each part to the total in a way that IMO, is maximum insight with minimum time and effort.
Here is a quick video of how to make that in Tableau:
All the charts can be found and downloaded here
2. Stacked bar Chart Alternative
Things get more complicated when we want to show part of a whole over time.
Here we are adding additional complexity and in fact we have multiple totals, each one has a different size and its own parts.
a very popular choice is to use stacked bar charts.
But again, this is not best practice.
The main issue here is that we can easily compare visually the lowest (West Region in the above example) but then the upper categories are not comparable because they simply not start from the same line.
My suggestion in this case is a line chart for each one of the categories and area chart to represent the total:
With this alternative our users get the ability compare the parts sizes as they all starts from 0 , we can also show how the totals changes over time and see for each period how each part’s portion contributes to the total.
Here is a quick video of how to make that in Tableau:
All the charts can be found and downloaded here
To wrap this up:
Thanks for reading, share your thoughts!
