This is the perfect video, if you would like to avoid creating charts like this one.
Or perhaps this one…
And especially this one
Being able to choose the right type of chart for the data you are working with is not an
exact science, but I’m sure you will agree something went wrong with these examples.
One can’t be certain whether they have been taken from a horror movie or a hippie fest.
In 99.9% of cases, we don’t want to show this to our audience.
Charts are an opportunity.
A storytelling tool.
A chance to make a convincing argument through visualizing data.
We are not going to convince anybody if we choose a type of chart that is not the right
fit for the data.
To help you overcome or avoid this issue, in this video we’ll discuss:
a) the different types of charts, and b) the type of data they are suitable for
Bar charts Probably the most frequently used type of
chart is the basic bar chart.
As its name suggests it is composed of a series of bars illustrating a variable’s development.
Given that bar charts are so common, people are generally familiar with them and can understand
them easily.
Examples like this one are straightforward to read.
However, please be aware that bar charts can be confusing, too.
Especially if one uses them to compare several variables.
I personally believe that a comparison of more than two variables with a clustered bar
chart becomes too cluttered.
Here is an example of a clustered bar chart that is not exactly crystal clear:
This isn’t a horrible visualization, but it leaves plenty to be desired.
First of all, it is difficult to follow the trend of all five variables simultaneously,
isn’t it?
Moreover, it is hard to gain an idea about the overall state of the Fiction Book Sales
market, and how it changed, which was probably what the person who created the chart wanted
to show in the first place.
When to use bar charts So, bar charts are nice, but limited.
We have to consider the type of data we want to visualize and the number of variables that
will be added to the chart.
Bar charts are great when we want to track the development of one or two variables over
time.
For example, one of the most frequent applications of bar charts in corporate presentations is
to show how a company’s total revenues have developed during a given period.
A bar chart can be used to make both a year-on-year comparison, and to provide a monthly breakdown.
Moreover, bar charts can be pretty intuitive when we compare the development of two numerical
variables over time.
Let’s say we would like to compare the revenues of two companies in the timeframe between
2014 and 2018.
When to avoid using bar charts Simple bar charts are far from ideal in situations
when we have several variables and all of them are part of a whole.
Such as the case In the Fiction Book Sales chart we showed you, there were five categories:
Young adult; classics; mystery; romance; and Sci-fi.
All of which account for all fiction books.
Meaning, their sum gives us the total volume of the Fiction book sales market.
Do we get any of this information with this bar chart?
We don’t.
It simply shows us multiple lines and one has to start making calculations on their
own to understand how numbers developed over time.
And if they have to do that, why bother creating a chart?
We are better off showing the data in a table format, right?
So, this certainly is one case where we should use a different type of chart.
Along the same lines, a simple bar chart isn’t suitable when we have a single period breakdown
of a variable.
If I want to portray the main business lines that contributed to a company’s revenues
in 2018, I wouldn’t use a bar chart.
Instead, I’d create a pie chart or one of its variations.
Pie charts A pie chart is a circular graph divided into
slices.
The larger a slice is, the bigger portion of the total quantity it represents.
When to use a pie chart So, pie charts are best suited to depict sections
of a whole.
What does that mean?
If a company operates three separate divisions, at year end its top management would be interested
in seeing what portion of total revenue each division accounted for.
A pie chart is perfect in this case.
However, we need to be certain that the sum of the proportions makes 100% of the total.
That is, we cannot afford to forget any of the three divisions contributing to total
revenue.
When to avoid pie charts Obviously, we can’t use a pie chart in situations
when we would like to show how a variable (or multiple variables) develops over time.
Pie charts are a definite no-go in these cases.
Moreover, as mentioned earlier, a pie chart would be misleading if we don’t consider
all values.
In the context of our example from earlier, we shouldn’t create a pie chart that includes
revenue of only two of the firm’s three divisions.
Doughnut charts Doughnut charts are basically pie charts with
a hole in the middle.
(It is as if their heart is missing…)
When to use doughnut charts The use cases of pie and doughnut charts are
identical.
The only important difference is that doughnut charts allow us to indicate the total amount
by adding a text box in the middle.
If you use a pie chart, you will have to include the total amount elsewhere (like adding it
to the title).
When to avoid using doughnut charts We already explained when to avoid using pie
charts.
The same is valid for doughnut charts.
One piece of advice when choosing whether to include a pie or a doughnut chart would
be to think of your audience.
How likely is it they would be interested in seeing the total figure for breakdown you
are providing?
If the split itself is more important, then go ahead and use a pie chart.
If the value of the total is important too, then perhaps a doughnut chart would be preferable.
Moreover, some studies have shown that people tend to get a distorted idea when shown pie
charts, as larger portions can look even more so because they cover more space.
With doughnut charts this isn’t as much of an issue.
Line charts A line chart is, as one can easily imagine,
a line or multiple lines showing how single, or multiple variables develop over time.
It is a great tool because we can easily highlight the magnitude of change of one or more variables
over a period.
When to use line charts Remember the awkward Fiction book sales chart
we saw earlier?
Well, a simple line chart would have been way better in that case.
A line chart allows us to track the development of several variables at the same time.
It is very easy to understand, and the reader doesn’t feel overwhelmed.
When to avoid line charts Line charts are not that great in situations
when you want to show how the individual parts of a whole change over time.
Yes, in theory one could use a stacked line chart (where line values accumulate) or a
100% stacked line chart (where lines accumulate to 100%), but a stacked area chart would look
better.
Area charts Area charts are very similar to line charts.
In fact, at first, I wanted to show them together.
However, one major confusion could have arisen.
So, please pay attention.
The idea of an area chart is based on the line chart.
Coloured regions (areas) show us the development of each variable over time.
There are three types of area charts: regular area chart, stacked area chart, and 100% stacked
area chart.
When to use an area chart Whenever we want to show how the parts of
a whole change over time, we should consider an area chart.
So, for example, if the company has three revenue generating divisions, it is very likely
that management would like to see the development of each of these divisions.
This is a great way to draw attention to the total value and still emphasize an important
trend – say, revenues from one division have been growing rapidly while the other
two have kept the same level.
A stacked area chart is perfect in this case.
However, if we are interested in the portion of revenue generated by each division and
not that much of the total amount of revenues, we can simply use a 100% stacked area chart.
This will show each division’s percentage contribution over time.
When to avoid area charts Obviously, similarly to line charts, area
charts are not suitable for representing parts of a whole over a single period.
In our example, we can’t use an area chart to show the proportion of revenues each division
generated in say, 2018 alone.
So that’s a situation where we can’t use an area chart.
In general, I would stay away from the classical area chart too.
It can be very confusing and even Microsoft themselves recommend avoiding it and to consider
using a simple line chart.
If we wanted to show the development of revenues generated by each of the firm’s divisions
over time with a simple area chart, we would have something looking like this.
I know.
A nightmare.
So, to recap.
Line and area charts function in a strange symbiosis between each other:
It is recommended to use the line chart, stacked area chart, and 100% stacked area chart;
We should avoid using: area chart, stacked line chart, and 100%-line chart
Ok, great!
We are doing really well.
Let’s make a short pause here and in our next video, we will discuss treemap, bridge,
scatter, and histogram charts.
Make sure you don’t miss it because it is a great one!